2 /* pngrtran.c - transforms the data in a row for PNG readers
4 * Last changed in libpng 1.6.9 [February 6, 2014]
5 * Copyright (c) 1998-2014 Glenn Randers-Pehrson
6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
13 * This file contains functions optionally called by an application
14 * in order to tell libpng how to handle data when reading a PNG.
15 * Transformations that are used in both reading and writing are
21 #ifdef PNG_READ_SUPPORTED
23 /* Set the action on getting a CRC error for an ancillary or critical chunk. */
25 png_set_crc_action(png_structrp png_ptr
, int crit_action
, int ancil_action
)
27 png_debug(1, "in png_set_crc_action");
32 /* Tell libpng how we react to CRC errors in critical chunks */
35 case PNG_CRC_NO_CHANGE
: /* Leave setting as is */
38 case PNG_CRC_WARN_USE
: /* Warn/use data */
39 png_ptr
->flags
&= ~PNG_FLAG_CRC_CRITICAL_MASK
;
40 png_ptr
->flags
|= PNG_FLAG_CRC_CRITICAL_USE
;
43 case PNG_CRC_QUIET_USE
: /* Quiet/use data */
44 png_ptr
->flags
&= ~PNG_FLAG_CRC_CRITICAL_MASK
;
45 png_ptr
->flags
|= PNG_FLAG_CRC_CRITICAL_USE
|
46 PNG_FLAG_CRC_CRITICAL_IGNORE
;
49 case PNG_CRC_WARN_DISCARD
: /* Not a valid action for critical data */
51 "Can't discard critical data on CRC error");
52 case PNG_CRC_ERROR_QUIT
: /* Error/quit */
56 png_ptr
->flags
&= ~PNG_FLAG_CRC_CRITICAL_MASK
;
60 /* Tell libpng how we react to CRC errors in ancillary chunks */
63 case PNG_CRC_NO_CHANGE
: /* Leave setting as is */
66 case PNG_CRC_WARN_USE
: /* Warn/use data */
67 png_ptr
->flags
&= ~PNG_FLAG_CRC_ANCILLARY_MASK
;
68 png_ptr
->flags
|= PNG_FLAG_CRC_ANCILLARY_USE
;
71 case PNG_CRC_QUIET_USE
: /* Quiet/use data */
72 png_ptr
->flags
&= ~PNG_FLAG_CRC_ANCILLARY_MASK
;
73 png_ptr
->flags
|= PNG_FLAG_CRC_ANCILLARY_USE
|
74 PNG_FLAG_CRC_ANCILLARY_NOWARN
;
77 case PNG_CRC_ERROR_QUIT
: /* Error/quit */
78 png_ptr
->flags
&= ~PNG_FLAG_CRC_ANCILLARY_MASK
;
79 png_ptr
->flags
|= PNG_FLAG_CRC_ANCILLARY_NOWARN
;
82 case PNG_CRC_WARN_DISCARD
: /* Warn/discard data */
86 png_ptr
->flags
&= ~PNG_FLAG_CRC_ANCILLARY_MASK
;
91 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
92 /* Is it OK to set a transformation now? Only if png_start_read_image or
93 * png_read_update_info have not been called. It is not necessary for the IHDR
94 * to have been read in all cases, the parameter allows for this check too.
97 png_rtran_ok(png_structrp png_ptr
, int need_IHDR
)
101 if (png_ptr
->flags
& PNG_FLAG_ROW_INIT
)
102 png_app_error(png_ptr
,
103 "invalid after png_start_read_image or png_read_update_info");
105 else if (need_IHDR
&& (png_ptr
->mode
& PNG_HAVE_IHDR
) == 0)
106 png_app_error(png_ptr
, "invalid before the PNG header has been read");
110 /* Turn on failure to initialize correctly for all transforms. */
111 png_ptr
->flags
|= PNG_FLAG_DETECT_UNINITIALIZED
;
117 return 0; /* no png_error possible! */
121 #ifdef PNG_READ_BACKGROUND_SUPPORTED
122 /* Handle alpha and tRNS via a background color */
124 png_set_background_fixed(png_structrp png_ptr
,
125 png_const_color_16p background_color
, int background_gamma_code
,
126 int need_expand
, png_fixed_point background_gamma
)
128 png_debug(1, "in png_set_background_fixed");
130 if (!png_rtran_ok(png_ptr
, 0) || background_color
== NULL
)
133 if (background_gamma_code
== PNG_BACKGROUND_GAMMA_UNKNOWN
)
135 png_warning(png_ptr
, "Application must supply a known background gamma");
139 png_ptr
->transformations
|= PNG_COMPOSE
| PNG_STRIP_ALPHA
;
140 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
141 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
143 png_ptr
->background
= *background_color
;
144 png_ptr
->background_gamma
= background_gamma
;
145 png_ptr
->background_gamma_type
= (png_byte
)(background_gamma_code
);
147 png_ptr
->transformations
|= PNG_BACKGROUND_EXPAND
;
149 png_ptr
->transformations
&= ~PNG_BACKGROUND_EXPAND
;
152 # ifdef PNG_FLOATING_POINT_SUPPORTED
154 png_set_background(png_structrp png_ptr
,
155 png_const_color_16p background_color
, int background_gamma_code
,
156 int need_expand
, double background_gamma
)
158 png_set_background_fixed(png_ptr
, background_color
, background_gamma_code
,
159 need_expand
, png_fixed(png_ptr
, background_gamma
, "png_set_background"));
161 # endif /* FLOATING_POINT */
162 #endif /* READ_BACKGROUND */
164 /* Scale 16-bit depth files to 8-bit depth. If both of these are set then the
165 * one that pngrtran does first (scale) happens. This is necessary to allow the
166 * TRANSFORM and API behavior to be somewhat consistent, and it's simpler.
168 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
170 png_set_scale_16(png_structrp png_ptr
)
172 png_debug(1, "in png_set_scale_16");
174 if (!png_rtran_ok(png_ptr
, 0))
177 png_ptr
->transformations
|= PNG_SCALE_16_TO_8
;
181 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
182 /* Chop 16-bit depth files to 8-bit depth */
184 png_set_strip_16(png_structrp png_ptr
)
186 png_debug(1, "in png_set_strip_16");
188 if (!png_rtran_ok(png_ptr
, 0))
191 png_ptr
->transformations
|= PNG_16_TO_8
;
195 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
197 png_set_strip_alpha(png_structrp png_ptr
)
199 png_debug(1, "in png_set_strip_alpha");
201 if (!png_rtran_ok(png_ptr
, 0))
204 png_ptr
->transformations
|= PNG_STRIP_ALPHA
;
208 #if defined(PNG_READ_ALPHA_MODE_SUPPORTED) || defined(PNG_READ_GAMMA_SUPPORTED)
209 static png_fixed_point
210 translate_gamma_flags(png_structrp png_ptr
, png_fixed_point output_gamma
,
213 /* Check for flag values. The main reason for having the old Mac value as a
214 * flag is that it is pretty near impossible to work out what the correct
215 * value is from Apple documentation - a working Mac system is needed to
216 * discover the value!
218 if (output_gamma
== PNG_DEFAULT_sRGB
||
219 output_gamma
== PNG_FP_1
/ PNG_DEFAULT_sRGB
)
221 /* If there is no sRGB support this just sets the gamma to the standard
222 * sRGB value. (This is a side effect of using this function!)
224 # ifdef PNG_READ_sRGB_SUPPORTED
225 png_ptr
->flags
|= PNG_FLAG_ASSUME_sRGB
;
230 output_gamma
= PNG_GAMMA_sRGB
;
232 output_gamma
= PNG_GAMMA_sRGB_INVERSE
;
235 else if (output_gamma
== PNG_GAMMA_MAC_18
||
236 output_gamma
== PNG_FP_1
/ PNG_GAMMA_MAC_18
)
239 output_gamma
= PNG_GAMMA_MAC_OLD
;
241 output_gamma
= PNG_GAMMA_MAC_INVERSE
;
247 # ifdef PNG_FLOATING_POINT_SUPPORTED
248 static png_fixed_point
249 convert_gamma_value(png_structrp png_ptr
, double output_gamma
)
251 /* The following silently ignores cases where fixed point (times 100,000)
252 * gamma values are passed to the floating point API. This is safe and it
253 * means the fixed point constants work just fine with the floating point
254 * API. The alternative would just lead to undetected errors and spurious
255 * bug reports. Negative values fail inside the _fixed API unless they
256 * correspond to the flag values.
258 if (output_gamma
> 0 && output_gamma
< 128)
259 output_gamma
*= PNG_FP_1
;
261 /* This preserves -1 and -2 exactly: */
262 output_gamma
= floor(output_gamma
+ .5);
264 if (output_gamma
> PNG_FP_MAX
|| output_gamma
< PNG_FP_MIN
)
265 png_fixed_error(png_ptr
, "gamma value");
267 return (png_fixed_point
)output_gamma
;
270 #endif /* READ_ALPHA_MODE || READ_GAMMA */
272 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
274 png_set_alpha_mode_fixed(png_structrp png_ptr
, int mode
,
275 png_fixed_point output_gamma
)
278 png_fixed_point file_gamma
;
280 png_debug(1, "in png_set_alpha_mode");
282 if (!png_rtran_ok(png_ptr
, 0))
285 output_gamma
= translate_gamma_flags(png_ptr
, output_gamma
, 1/*screen*/);
287 /* Validate the value to ensure it is in a reasonable range. The value
288 * is expected to be 1 or greater, but this range test allows for some
289 * viewing correction values. The intent is to weed out users of this API
290 * who use the inverse of the gamma value accidentally! Since some of these
291 * values are reasonable this may have to be changed.
293 if (output_gamma
< 70000 || output_gamma
> 300000)
294 png_error(png_ptr
, "output gamma out of expected range");
296 /* The default file gamma is the inverse of the output gamma; the output
297 * gamma may be changed below so get the file value first:
299 file_gamma
= png_reciprocal(output_gamma
);
301 /* There are really 8 possibilities here, composed of any combination
304 * premultiply the color channels
305 * do not encode non-opaque pixels
306 * encode the alpha as well as the color channels
308 * The differences disappear if the input/output ('screen') gamma is 1.0,
309 * because then the encoding is a no-op and there is only the choice of
310 * premultiplying the color channels or not.
312 * png_set_alpha_mode and png_set_background interact because both use
313 * png_compose to do the work. Calling both is only useful when
314 * png_set_alpha_mode is used to set the default mode - PNG_ALPHA_PNG - along
315 * with a default gamma value. Otherwise PNG_COMPOSE must not be set.
319 case PNG_ALPHA_PNG
: /* default: png standard */
320 /* No compose, but it may be set by png_set_background! */
321 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
322 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
325 case PNG_ALPHA_ASSOCIATED
: /* color channels premultiplied */
327 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
328 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
329 /* The output is linear: */
330 output_gamma
= PNG_FP_1
;
333 case PNG_ALPHA_OPTIMIZED
: /* associated, non-opaque pixels linear */
335 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
336 png_ptr
->flags
|= PNG_FLAG_OPTIMIZE_ALPHA
;
337 /* output_gamma records the encoding of opaque pixels! */
340 case PNG_ALPHA_BROKEN
: /* associated, non-linear, alpha encoded */
342 png_ptr
->transformations
|= PNG_ENCODE_ALPHA
;
343 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
347 png_error(png_ptr
, "invalid alpha mode");
350 /* Only set the default gamma if the file gamma has not been set (this has
351 * the side effect that the gamma in a second call to png_set_alpha_mode will
354 if (png_ptr
->colorspace
.gamma
== 0)
356 png_ptr
->colorspace
.gamma
= file_gamma
;
357 png_ptr
->colorspace
.flags
|= PNG_COLORSPACE_HAVE_GAMMA
;
360 /* But always set the output gamma: */
361 png_ptr
->screen_gamma
= output_gamma
;
363 /* Finally, if pre-multiplying, set the background fields to achieve the
368 /* And obtain alpha pre-multiplication by composing on black: */
369 memset(&png_ptr
->background
, 0, (sizeof png_ptr
->background
));
370 png_ptr
->background_gamma
= png_ptr
->colorspace
.gamma
; /* just in case */
371 png_ptr
->background_gamma_type
= PNG_BACKGROUND_GAMMA_FILE
;
372 png_ptr
->transformations
&= ~PNG_BACKGROUND_EXPAND
;
374 if (png_ptr
->transformations
& PNG_COMPOSE
)
376 "conflicting calls to set alpha mode and background");
378 png_ptr
->transformations
|= PNG_COMPOSE
;
382 # ifdef PNG_FLOATING_POINT_SUPPORTED
384 png_set_alpha_mode(png_structrp png_ptr
, int mode
, double output_gamma
)
386 png_set_alpha_mode_fixed(png_ptr
, mode
, convert_gamma_value(png_ptr
,
392 #ifdef PNG_READ_QUANTIZE_SUPPORTED
393 /* Dither file to 8-bit. Supply a palette, the current number
394 * of elements in the palette, the maximum number of elements
395 * allowed, and a histogram if possible. If the current number
396 * of colors is greater then the maximum number, the palette will be
397 * modified to fit in the maximum number. "full_quantize" indicates
398 * whether we need a quantizing cube set up for RGB images, or if we
399 * simply are reducing the number of colors in a paletted image.
402 typedef struct png_dsort_struct
404 struct png_dsort_struct
* next
;
408 typedef png_dsort
* png_dsortp
;
409 typedef png_dsort
* * png_dsortpp
;
412 png_set_quantize(png_structrp png_ptr
, png_colorp palette
,
413 int num_palette
, int maximum_colors
, png_const_uint_16p histogram
,
416 png_debug(1, "in png_set_quantize");
418 if (!png_rtran_ok(png_ptr
, 0))
421 png_ptr
->transformations
|= PNG_QUANTIZE
;
427 png_ptr
->quantize_index
= (png_bytep
)png_malloc(png_ptr
,
428 (png_uint_32
)(num_palette
* (sizeof (png_byte
))));
429 for (i
= 0; i
< num_palette
; i
++)
430 png_ptr
->quantize_index
[i
] = (png_byte
)i
;
433 if (num_palette
> maximum_colors
)
435 if (histogram
!= NULL
)
437 /* This is easy enough, just throw out the least used colors.
438 * Perhaps not the best solution, but good enough.
443 /* Initialize an array to sort colors */
444 png_ptr
->quantize_sort
= (png_bytep
)png_malloc(png_ptr
,
445 (png_uint_32
)(num_palette
* (sizeof (png_byte
))));
447 /* Initialize the quantize_sort array */
448 for (i
= 0; i
< num_palette
; i
++)
449 png_ptr
->quantize_sort
[i
] = (png_byte
)i
;
451 /* Find the least used palette entries by starting a
452 * bubble sort, and running it until we have sorted
453 * out enough colors. Note that we don't care about
454 * sorting all the colors, just finding which are
458 for (i
= num_palette
- 1; i
>= maximum_colors
; i
--)
460 int done
; /* To stop early if the list is pre-sorted */
464 for (j
= 0; j
< i
; j
++)
466 if (histogram
[png_ptr
->quantize_sort
[j
]]
467 < histogram
[png_ptr
->quantize_sort
[j
+ 1]])
471 t
= png_ptr
->quantize_sort
[j
];
472 png_ptr
->quantize_sort
[j
] = png_ptr
->quantize_sort
[j
+ 1];
473 png_ptr
->quantize_sort
[j
+ 1] = t
;
482 /* Swap the palette around, and set up a table, if necessary */
487 /* Put all the useful colors within the max, but don't
490 for (i
= 0; i
< maximum_colors
; i
++)
492 if ((int)png_ptr
->quantize_sort
[i
] >= maximum_colors
)
496 while ((int)png_ptr
->quantize_sort
[j
] >= maximum_colors
);
498 palette
[i
] = palette
[j
];
506 /* Move all the used colors inside the max limit, and
507 * develop a translation table.
509 for (i
= 0; i
< maximum_colors
; i
++)
511 /* Only move the colors we need to */
512 if ((int)png_ptr
->quantize_sort
[i
] >= maximum_colors
)
518 while ((int)png_ptr
->quantize_sort
[j
] >= maximum_colors
);
520 tmp_color
= palette
[j
];
521 palette
[j
] = palette
[i
];
522 palette
[i
] = tmp_color
;
523 /* Indicate where the color went */
524 png_ptr
->quantize_index
[j
] = (png_byte
)i
;
525 png_ptr
->quantize_index
[i
] = (png_byte
)j
;
529 /* Find closest color for those colors we are not using */
530 for (i
= 0; i
< num_palette
; i
++)
532 if ((int)png_ptr
->quantize_index
[i
] >= maximum_colors
)
534 int min_d
, k
, min_k
, d_index
;
536 /* Find the closest color to one we threw out */
537 d_index
= png_ptr
->quantize_index
[i
];
538 min_d
= PNG_COLOR_DIST(palette
[d_index
], palette
[0]);
539 for (k
= 1, min_k
= 0; k
< maximum_colors
; k
++)
543 d
= PNG_COLOR_DIST(palette
[d_index
], palette
[k
]);
551 /* Point to closest color */
552 png_ptr
->quantize_index
[i
] = (png_byte
)min_k
;
556 png_free(png_ptr
, png_ptr
->quantize_sort
);
557 png_ptr
->quantize_sort
= NULL
;
561 /* This is much harder to do simply (and quickly). Perhaps
562 * we need to go through a median cut routine, but those
563 * don't always behave themselves with only a few colors
564 * as input. So we will just find the closest two colors,
565 * and throw out one of them (chosen somewhat randomly).
566 * [We don't understand this at all, so if someone wants to
567 * work on improving it, be our guest - AED, GRP]
577 /* Initialize palette index arrays */
578 png_ptr
->index_to_palette
= (png_bytep
)png_malloc(png_ptr
,
579 (png_uint_32
)(num_palette
* (sizeof (png_byte
))));
580 png_ptr
->palette_to_index
= (png_bytep
)png_malloc(png_ptr
,
581 (png_uint_32
)(num_palette
* (sizeof (png_byte
))));
583 /* Initialize the sort array */
584 for (i
= 0; i
< num_palette
; i
++)
586 png_ptr
->index_to_palette
[i
] = (png_byte
)i
;
587 png_ptr
->palette_to_index
[i
] = (png_byte
)i
;
590 hash
= (png_dsortpp
)png_calloc(png_ptr
, (png_uint_32
)(769 *
591 (sizeof (png_dsortp
))));
593 num_new_palette
= num_palette
;
595 /* Initial wild guess at how far apart the farthest pixel
596 * pair we will be eliminating will be. Larger
597 * numbers mean more areas will be allocated, Smaller
598 * numbers run the risk of not saving enough data, and
599 * having to do this all over again.
601 * I have not done extensive checking on this number.
605 while (num_new_palette
> maximum_colors
)
607 for (i
= 0; i
< num_new_palette
- 1; i
++)
611 for (j
= i
+ 1; j
< num_new_palette
; j
++)
615 d
= PNG_COLOR_DIST(palette
[i
], palette
[j
]);
620 t
= (png_dsortp
)png_malloc_warn(png_ptr
,
621 (png_uint_32
)(sizeof (png_dsort
)));
627 t
->left
= (png_byte
)i
;
628 t
->right
= (png_byte
)j
;
637 for (i
= 0; i
<= max_d
; i
++)
643 for (p
= hash
[i
]; p
; p
= p
->next
)
645 if ((int)png_ptr
->index_to_palette
[p
->left
]
647 (int)png_ptr
->index_to_palette
[p
->right
]
652 if (num_new_palette
& 0x01)
664 palette
[png_ptr
->index_to_palette
[j
]]
665 = palette
[num_new_palette
];
670 for (k
= 0; k
< num_palette
; k
++)
672 if (png_ptr
->quantize_index
[k
] ==
673 png_ptr
->index_to_palette
[j
])
674 png_ptr
->quantize_index
[k
] =
675 png_ptr
->index_to_palette
[next_j
];
677 if ((int)png_ptr
->quantize_index
[k
] ==
679 png_ptr
->quantize_index
[k
] =
680 png_ptr
->index_to_palette
[j
];
684 png_ptr
->index_to_palette
[png_ptr
->palette_to_index
685 [num_new_palette
]] = png_ptr
->index_to_palette
[j
];
687 png_ptr
->palette_to_index
[png_ptr
->index_to_palette
[j
]]
688 = png_ptr
->palette_to_index
[num_new_palette
];
690 png_ptr
->index_to_palette
[j
] =
691 (png_byte
)num_new_palette
;
693 png_ptr
->palette_to_index
[num_new_palette
] =
696 if (num_new_palette
<= maximum_colors
)
699 if (num_new_palette
<= maximum_colors
)
704 for (i
= 0; i
< 769; i
++)
708 png_dsortp p
= hash
[i
];
712 png_free(png_ptr
, p
);
720 png_free(png_ptr
, hash
);
721 png_free(png_ptr
, png_ptr
->palette_to_index
);
722 png_free(png_ptr
, png_ptr
->index_to_palette
);
723 png_ptr
->palette_to_index
= NULL
;
724 png_ptr
->index_to_palette
= NULL
;
726 num_palette
= maximum_colors
;
728 if (png_ptr
->palette
== NULL
)
730 png_ptr
->palette
= palette
;
732 png_ptr
->num_palette
= (png_uint_16
)num_palette
;
738 int total_bits
= PNG_QUANTIZE_RED_BITS
+ PNG_QUANTIZE_GREEN_BITS
+
739 PNG_QUANTIZE_BLUE_BITS
;
740 int num_red
= (1 << PNG_QUANTIZE_RED_BITS
);
741 int num_green
= (1 << PNG_QUANTIZE_GREEN_BITS
);
742 int num_blue
= (1 << PNG_QUANTIZE_BLUE_BITS
);
743 png_size_t num_entries
= ((png_size_t
)1 << total_bits
);
745 png_ptr
->palette_lookup
= (png_bytep
)png_calloc(png_ptr
,
746 (png_uint_32
)(num_entries
* (sizeof (png_byte
))));
748 distance
= (png_bytep
)png_malloc(png_ptr
, (png_uint_32
)(num_entries
*
749 (sizeof (png_byte
))));
751 memset(distance
, 0xff, num_entries
* (sizeof (png_byte
)));
753 for (i
= 0; i
< num_palette
; i
++)
756 int r
= (palette
[i
].red
>> (8 - PNG_QUANTIZE_RED_BITS
));
757 int g
= (palette
[i
].green
>> (8 - PNG_QUANTIZE_GREEN_BITS
));
758 int b
= (palette
[i
].blue
>> (8 - PNG_QUANTIZE_BLUE_BITS
));
760 for (ir
= 0; ir
< num_red
; ir
++)
762 /* int dr = abs(ir - r); */
763 int dr
= ((ir
> r
) ? ir
- r
: r
- ir
);
764 int index_r
= (ir
<< (PNG_QUANTIZE_BLUE_BITS
+
765 PNG_QUANTIZE_GREEN_BITS
));
767 for (ig
= 0; ig
< num_green
; ig
++)
769 /* int dg = abs(ig - g); */
770 int dg
= ((ig
> g
) ? ig
- g
: g
- ig
);
772 int dm
= ((dr
> dg
) ? dr
: dg
);
773 int index_g
= index_r
| (ig
<< PNG_QUANTIZE_BLUE_BITS
);
775 for (ib
= 0; ib
< num_blue
; ib
++)
777 int d_index
= index_g
| ib
;
778 /* int db = abs(ib - b); */
779 int db
= ((ib
> b
) ? ib
- b
: b
- ib
);
780 int dmax
= ((dm
> db
) ? dm
: db
);
781 int d
= dmax
+ dt
+ db
;
783 if (d
< (int)distance
[d_index
])
785 distance
[d_index
] = (png_byte
)d
;
786 png_ptr
->palette_lookup
[d_index
] = (png_byte
)i
;
793 png_free(png_ptr
, distance
);
796 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
798 #ifdef PNG_READ_GAMMA_SUPPORTED
800 png_set_gamma_fixed(png_structrp png_ptr
, png_fixed_point scrn_gamma
,
801 png_fixed_point file_gamma
)
803 png_debug(1, "in png_set_gamma_fixed");
805 if (!png_rtran_ok(png_ptr
, 0))
808 /* New in libpng-1.5.4 - reserve particular negative values as flags. */
809 scrn_gamma
= translate_gamma_flags(png_ptr
, scrn_gamma
, 1/*screen*/);
810 file_gamma
= translate_gamma_flags(png_ptr
, file_gamma
, 0/*file*/);
812 /* Checking the gamma values for being >0 was added in 1.5.4 along with the
813 * premultiplied alpha support; this actually hides an undocumented feature
814 * of the previous implementation which allowed gamma processing to be
815 * disabled in background handling. There is no evidence (so far) that this
816 * was being used; however, png_set_background itself accepted and must still
817 * accept '0' for the gamma value it takes, because it isn't always used.
819 * Since this is an API change (albeit a very minor one that removes an
820 * undocumented API feature) the following checks were only enabled in
824 png_error(png_ptr
, "invalid file gamma in png_set_gamma");
827 png_error(png_ptr
, "invalid screen gamma in png_set_gamma");
829 /* Set the gamma values unconditionally - this overrides the value in the PNG
830 * file if a gAMA chunk was present. png_set_alpha_mode provides a
831 * different, easier, way to default the file gamma.
833 png_ptr
->colorspace
.gamma
= file_gamma
;
834 png_ptr
->colorspace
.flags
|= PNG_COLORSPACE_HAVE_GAMMA
;
835 png_ptr
->screen_gamma
= scrn_gamma
;
838 # ifdef PNG_FLOATING_POINT_SUPPORTED
840 png_set_gamma(png_structrp png_ptr
, double scrn_gamma
, double file_gamma
)
842 png_set_gamma_fixed(png_ptr
, convert_gamma_value(png_ptr
, scrn_gamma
),
843 convert_gamma_value(png_ptr
, file_gamma
));
845 # endif /* FLOATING_POINT_SUPPORTED */
846 #endif /* READ_GAMMA */
848 #ifdef PNG_READ_EXPAND_SUPPORTED
849 /* Expand paletted images to RGB, expand grayscale images of
850 * less than 8-bit depth to 8-bit depth, and expand tRNS chunks
854 png_set_expand(png_structrp png_ptr
)
856 png_debug(1, "in png_set_expand");
858 if (!png_rtran_ok(png_ptr
, 0))
861 png_ptr
->transformations
|= (PNG_EXPAND
| PNG_EXPAND_tRNS
);
864 /* GRR 19990627: the following three functions currently are identical
865 * to png_set_expand(). However, it is entirely reasonable that someone
866 * might wish to expand an indexed image to RGB but *not* expand a single,
867 * fully transparent palette entry to a full alpha channel--perhaps instead
868 * convert tRNS to the grayscale/RGB format (16-bit RGB value), or replace
869 * the transparent color with a particular RGB value, or drop tRNS entirely.
870 * IOW, a future version of the library may make the transformations flag
871 * a bit more fine-grained, with separate bits for each of these three
874 * More to the point, these functions make it obvious what libpng will be
875 * doing, whereas "expand" can (and does) mean any number of things.
877 * GRP 20060307: In libpng-1.2.9, png_set_gray_1_2_4_to_8() was modified
878 * to expand only the sample depth but not to expand the tRNS to alpha
879 * and its name was changed to png_set_expand_gray_1_2_4_to_8().
882 /* Expand paletted images to RGB. */
884 png_set_palette_to_rgb(png_structrp png_ptr
)
886 png_debug(1, "in png_set_palette_to_rgb");
888 if (!png_rtran_ok(png_ptr
, 0))
891 png_ptr
->transformations
|= (PNG_EXPAND
| PNG_EXPAND_tRNS
);
894 /* Expand grayscale images of less than 8-bit depth to 8 bits. */
896 png_set_expand_gray_1_2_4_to_8(png_structrp png_ptr
)
898 png_debug(1, "in png_set_expand_gray_1_2_4_to_8");
900 if (!png_rtran_ok(png_ptr
, 0))
903 png_ptr
->transformations
|= PNG_EXPAND
;
906 /* Expand tRNS chunks to alpha channels. */
908 png_set_tRNS_to_alpha(png_structrp png_ptr
)
910 png_debug(1, "in png_set_tRNS_to_alpha");
912 if (!png_rtran_ok(png_ptr
, 0))
915 png_ptr
->transformations
|= (PNG_EXPAND
| PNG_EXPAND_tRNS
);
917 #endif /* defined(PNG_READ_EXPAND_SUPPORTED) */
919 #ifdef PNG_READ_EXPAND_16_SUPPORTED
920 /* Expand to 16-bit channels, expand the tRNS chunk too (because otherwise
921 * it may not work correctly.)
924 png_set_expand_16(png_structrp png_ptr
)
926 png_debug(1, "in png_set_expand_16");
928 if (!png_rtran_ok(png_ptr
, 0))
931 png_ptr
->transformations
|= (PNG_EXPAND_16
| PNG_EXPAND
| PNG_EXPAND_tRNS
);
935 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
937 png_set_gray_to_rgb(png_structrp png_ptr
)
939 png_debug(1, "in png_set_gray_to_rgb");
941 if (!png_rtran_ok(png_ptr
, 0))
944 /* Because rgb must be 8 bits or more: */
945 png_set_expand_gray_1_2_4_to_8(png_ptr
);
946 png_ptr
->transformations
|= PNG_GRAY_TO_RGB
;
950 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
952 png_set_rgb_to_gray_fixed(png_structrp png_ptr
, int error_action
,
953 png_fixed_point red
, png_fixed_point green
)
955 png_debug(1, "in png_set_rgb_to_gray");
957 /* Need the IHDR here because of the check on color_type below. */
959 if (!png_rtran_ok(png_ptr
, 1))
964 case PNG_ERROR_ACTION_NONE
:
965 png_ptr
->transformations
|= PNG_RGB_TO_GRAY
;
968 case PNG_ERROR_ACTION_WARN
:
969 png_ptr
->transformations
|= PNG_RGB_TO_GRAY_WARN
;
972 case PNG_ERROR_ACTION_ERROR
:
973 png_ptr
->transformations
|= PNG_RGB_TO_GRAY_ERR
;
977 png_error(png_ptr
, "invalid error action to rgb_to_gray");
981 if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
982 #ifdef PNG_READ_EXPAND_SUPPORTED
983 png_ptr
->transformations
|= PNG_EXPAND
;
986 /* Make this an error in 1.6 because otherwise the application may assume
987 * that it just worked and get a memory overwrite.
990 "Cannot do RGB_TO_GRAY without EXPAND_SUPPORTED");
992 /* png_ptr->transformations &= ~PNG_RGB_TO_GRAY; */
996 if (red
>= 0 && green
>= 0 && red
+ green
<= PNG_FP_1
)
998 png_uint_16 red_int
, green_int
;
1000 /* NOTE: this calculation does not round, but this behavior is retained
1001 * for consistency, the inaccuracy is very small. The code here always
1002 * overwrites the coefficients, regardless of whether they have been
1003 * defaulted or set already.
1005 red_int
= (png_uint_16
)(((png_uint_32
)red
*32768)/100000);
1006 green_int
= (png_uint_16
)(((png_uint_32
)green
*32768)/100000);
1008 png_ptr
->rgb_to_gray_red_coeff
= red_int
;
1009 png_ptr
->rgb_to_gray_green_coeff
= green_int
;
1010 png_ptr
->rgb_to_gray_coefficients_set
= 1;
1015 if (red
>= 0 && green
>= 0)
1016 png_app_warning(png_ptr
,
1017 "ignoring out of range rgb_to_gray coefficients");
1019 /* Use the defaults, from the cHRM chunk if set, else the historical
1020 * values which are close to the sRGB/HDTV/ITU-Rec 709 values. See
1021 * png_do_rgb_to_gray for more discussion of the values. In this case
1022 * the coefficients are not marked as 'set' and are not overwritten if
1023 * something has already provided a default.
1025 if (png_ptr
->rgb_to_gray_red_coeff
== 0 &&
1026 png_ptr
->rgb_to_gray_green_coeff
== 0)
1028 png_ptr
->rgb_to_gray_red_coeff
= 6968;
1029 png_ptr
->rgb_to_gray_green_coeff
= 23434;
1030 /* png_ptr->rgb_to_gray_blue_coeff = 2366; */
1036 #ifdef PNG_FLOATING_POINT_SUPPORTED
1037 /* Convert a RGB image to a grayscale of the same width. This allows us,
1038 * for example, to convert a 24 bpp RGB image into an 8 bpp grayscale image.
1042 png_set_rgb_to_gray(png_structrp png_ptr
, int error_action
, double red
,
1045 png_set_rgb_to_gray_fixed(png_ptr
, error_action
,
1046 png_fixed(png_ptr
, red
, "rgb to gray red coefficient"),
1047 png_fixed(png_ptr
, green
, "rgb to gray green coefficient"));
1049 #endif /* FLOATING POINT */
1051 #endif /* RGB_TO_GRAY */
1053 #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
1054 defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
1056 png_set_read_user_transform_fn(png_structrp png_ptr
, png_user_transform_ptr
1057 read_user_transform_fn
)
1059 png_debug(1, "in png_set_read_user_transform_fn");
1061 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
1062 png_ptr
->transformations
|= PNG_USER_TRANSFORM
;
1063 png_ptr
->read_user_transform_fn
= read_user_transform_fn
;
1068 #ifdef PNG_READ_TRANSFORMS_SUPPORTED
1069 #ifdef PNG_READ_GAMMA_SUPPORTED
1070 /* In the case of gamma transformations only do transformations on images where
1071 * the [file] gamma and screen_gamma are not close reciprocals, otherwise it
1072 * slows things down slightly, and also needlessly introduces small errors.
1074 static int /* PRIVATE */
1075 png_gamma_threshold(png_fixed_point screen_gamma
, png_fixed_point file_gamma
)
1077 /* PNG_GAMMA_THRESHOLD is the threshold for performing gamma
1078 * correction as a difference of the overall transform from 1.0
1080 * We want to compare the threshold with s*f - 1, if we get
1081 * overflow here it is because of wacky gamma values so we
1082 * turn on processing anyway.
1084 png_fixed_point gtest
;
1085 return !png_muldiv(>est
, screen_gamma
, file_gamma
, PNG_FP_1
) ||
1086 png_gamma_significant(gtest
);
1090 /* Initialize everything needed for the read. This includes modifying
1094 /*For the moment 'png_init_palette_transformations' and
1095 * 'png_init_rgb_transformations' only do some flag canceling optimizations.
1096 * The intent is that these two routines should have palette or rgb operations
1097 * extracted from 'png_init_read_transformations'.
1099 static void /* PRIVATE */
1100 png_init_palette_transformations(png_structrp png_ptr
)
1102 /* Called to handle the (input) palette case. In png_do_read_transformations
1103 * the first step is to expand the palette if requested, so this code must
1104 * take care to only make changes that are invariant with respect to the
1105 * palette expansion, or only do them if there is no expansion.
1107 * STRIP_ALPHA has already been handled in the caller (by setting num_trans
1110 int input_has_alpha
= 0;
1111 int input_has_transparency
= 0;
1113 if (png_ptr
->num_trans
> 0)
1117 /* Ignore if all the entries are opaque (unlikely!) */
1118 for (i
=0; i
<png_ptr
->num_trans
; ++i
)
1120 if (png_ptr
->trans_alpha
[i
] == 255)
1122 else if (png_ptr
->trans_alpha
[i
] == 0)
1123 input_has_transparency
= 1;
1126 input_has_transparency
= 1;
1127 input_has_alpha
= 1;
1133 /* If no alpha we can optimize. */
1134 if (!input_has_alpha
)
1136 /* Any alpha means background and associative alpha processing is
1137 * required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
1138 * and ENCODE_ALPHA are irrelevant.
1140 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
1141 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
1143 if (!input_has_transparency
)
1144 png_ptr
->transformations
&= ~(PNG_COMPOSE
| PNG_BACKGROUND_EXPAND
);
1147 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1148 /* png_set_background handling - deals with the complexity of whether the
1149 * background color is in the file format or the screen format in the case
1150 * where an 'expand' will happen.
1153 /* The following code cannot be entered in the alpha pre-multiplication case
1154 * because PNG_BACKGROUND_EXPAND is cancelled below.
1156 if ((png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) &&
1157 (png_ptr
->transformations
& PNG_EXPAND
))
1160 png_ptr
->background
.red
=
1161 png_ptr
->palette
[png_ptr
->background
.index
].red
;
1162 png_ptr
->background
.green
=
1163 png_ptr
->palette
[png_ptr
->background
.index
].green
;
1164 png_ptr
->background
.blue
=
1165 png_ptr
->palette
[png_ptr
->background
.index
].blue
;
1167 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
1168 if (png_ptr
->transformations
& PNG_INVERT_ALPHA
)
1170 if (!(png_ptr
->transformations
& PNG_EXPAND_tRNS
))
1172 /* Invert the alpha channel (in tRNS) unless the pixels are
1173 * going to be expanded, in which case leave it for later
1175 int i
, istop
= png_ptr
->num_trans
;
1177 for (i
=0; i
<istop
; i
++)
1178 png_ptr
->trans_alpha
[i
] = (png_byte
)(255 -
1179 png_ptr
->trans_alpha
[i
]);
1182 #endif /* PNG_READ_INVERT_ALPHA_SUPPORTED */
1184 } /* background expand and (therefore) no alpha association. */
1185 #endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
1188 static void /* PRIVATE */
1189 png_init_rgb_transformations(png_structrp png_ptr
)
1191 /* Added to libpng-1.5.4: check the color type to determine whether there
1192 * is any alpha or transparency in the image and simply cancel the
1193 * background and alpha mode stuff if there isn't.
1195 int input_has_alpha
= (png_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0;
1196 int input_has_transparency
= png_ptr
->num_trans
> 0;
1198 /* If no alpha we can optimize. */
1199 if (!input_has_alpha
)
1201 /* Any alpha means background and associative alpha processing is
1202 * required, however if the alpha is 0 or 1 throughout OPTIMIZE_ALPHA
1203 * and ENCODE_ALPHA are irrelevant.
1205 # ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1206 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
1207 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
1210 if (!input_has_transparency
)
1211 png_ptr
->transformations
&= ~(PNG_COMPOSE
| PNG_BACKGROUND_EXPAND
);
1214 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1215 /* png_set_background handling - deals with the complexity of whether the
1216 * background color is in the file format or the screen format in the case
1217 * where an 'expand' will happen.
1220 /* The following code cannot be entered in the alpha pre-multiplication case
1221 * because PNG_BACKGROUND_EXPAND is cancelled below.
1223 if ((png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) &&
1224 (png_ptr
->transformations
& PNG_EXPAND
) &&
1225 !(png_ptr
->color_type
& PNG_COLOR_MASK_COLOR
))
1226 /* i.e., GRAY or GRAY_ALPHA */
1229 /* Expand background and tRNS chunks */
1230 int gray
= png_ptr
->background
.gray
;
1231 int trans_gray
= png_ptr
->trans_color
.gray
;
1233 switch (png_ptr
->bit_depth
)
1253 /* FALL THROUGH (Already 8 bits) */
1256 /* Already a full 16 bits */
1260 png_ptr
->background
.red
= png_ptr
->background
.green
=
1261 png_ptr
->background
.blue
= (png_uint_16
)gray
;
1263 if (!(png_ptr
->transformations
& PNG_EXPAND_tRNS
))
1265 png_ptr
->trans_color
.red
= png_ptr
->trans_color
.green
=
1266 png_ptr
->trans_color
.blue
= (png_uint_16
)trans_gray
;
1269 } /* background expand and (therefore) no alpha association. */
1270 #endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
1274 png_init_read_transformations(png_structrp png_ptr
)
1276 png_debug(1, "in png_init_read_transformations");
1278 /* This internal function is called from png_read_start_row in pngrutil.c
1279 * and it is called before the 'rowbytes' calculation is done, so the code
1280 * in here can change or update the transformations flags.
1282 * First do updates that do not depend on the details of the PNG image data
1286 #ifdef PNG_READ_GAMMA_SUPPORTED
1287 /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
1288 * png_set_alpha_mode and this is another source for a default file gamma so
1289 * the test needs to be performed later - here. In addition prior to 1.5.4
1290 * the tests were repeated for the PALETTE color type here - this is no
1291 * longer necessary (and doesn't seem to have been necessary before.)
1294 /* The following temporary indicates if overall gamma correction is
1297 int gamma_correction
= 0;
1299 if (png_ptr
->colorspace
.gamma
!= 0) /* has been set */
1301 if (png_ptr
->screen_gamma
!= 0) /* screen set too */
1302 gamma_correction
= png_gamma_threshold(png_ptr
->colorspace
.gamma
,
1303 png_ptr
->screen_gamma
);
1306 /* Assume the output matches the input; a long time default behavior
1307 * of libpng, although the standard has nothing to say about this.
1309 png_ptr
->screen_gamma
= png_reciprocal(png_ptr
->colorspace
.gamma
);
1312 else if (png_ptr
->screen_gamma
!= 0)
1313 /* The converse - assume the file matches the screen, note that this
1314 * perhaps undesireable default can (from 1.5.4) be changed by calling
1315 * png_set_alpha_mode (even if the alpha handling mode isn't required
1316 * or isn't changed from the default.)
1318 png_ptr
->colorspace
.gamma
= png_reciprocal(png_ptr
->screen_gamma
);
1320 else /* neither are set */
1321 /* Just in case the following prevents any processing - file and screen
1322 * are both assumed to be linear and there is no way to introduce a
1323 * third gamma value other than png_set_background with 'UNIQUE', and,
1326 png_ptr
->screen_gamma
= png_ptr
->colorspace
.gamma
= PNG_FP_1
;
1328 /* We have a gamma value now. */
1329 png_ptr
->colorspace
.flags
|= PNG_COLORSPACE_HAVE_GAMMA
;
1331 /* Now turn the gamma transformation on or off as appropriate. Notice
1332 * that PNG_GAMMA just refers to the file->screen correction. Alpha
1333 * composition may independently cause gamma correction because it needs
1334 * linear data (e.g. if the file has a gAMA chunk but the screen gamma
1335 * hasn't been specified.) In any case this flag may get turned off in
1336 * the code immediately below if the transform can be handled outside the
1339 if (gamma_correction
)
1340 png_ptr
->transformations
|= PNG_GAMMA
;
1343 png_ptr
->transformations
&= ~PNG_GAMMA
;
1347 /* Certain transformations have the effect of preventing other
1348 * transformations that happen afterward in png_do_read_transformations,
1349 * resolve the interdependencies here. From the code of
1350 * png_do_read_transformations the order is:
1352 * 1) PNG_EXPAND (including PNG_EXPAND_tRNS)
1353 * 2) PNG_STRIP_ALPHA (if no compose)
1354 * 3) PNG_RGB_TO_GRAY
1355 * 4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
1358 * 7) PNG_STRIP_ALPHA (if compose)
1359 * 8) PNG_ENCODE_ALPHA
1360 * 9) PNG_SCALE_16_TO_8
1362 * 11) PNG_QUANTIZE (converts to palette)
1364 * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
1365 * 14) PNG_INVERT_MONO
1370 * 19) PNG_FILLER (includes PNG_ADD_ALPHA)
1371 * 20) PNG_INVERT_ALPHA
1372 * 21) PNG_SWAP_ALPHA
1373 * 22) PNG_SWAP_BYTES
1374 * 23) PNG_USER_TRANSFORM [must be last]
1376 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
1377 if ((png_ptr
->transformations
& PNG_STRIP_ALPHA
) &&
1378 !(png_ptr
->transformations
& PNG_COMPOSE
))
1380 /* Stripping the alpha channel happens immediately after the 'expand'
1381 * transformations, before all other transformation, so it cancels out
1382 * the alpha handling. It has the side effect negating the effect of
1383 * PNG_EXPAND_tRNS too:
1385 png_ptr
->transformations
&= ~(PNG_BACKGROUND_EXPAND
| PNG_ENCODE_ALPHA
|
1387 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
1389 /* Kill the tRNS chunk itself too. Prior to 1.5.4 this did not happen
1390 * so transparency information would remain just so long as it wasn't
1391 * expanded. This produces unexpected API changes if the set of things
1392 * that do PNG_EXPAND_tRNS changes (perfectly possible given the
1393 * documentation - which says ask for what you want, accept what you
1394 * get.) This makes the behavior consistent from 1.5.4:
1396 png_ptr
->num_trans
= 0;
1398 #endif /* STRIP_ALPHA supported, no COMPOSE */
1400 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
1401 /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
1402 * settings will have no effect.
1404 if (!png_gamma_significant(png_ptr
->screen_gamma
))
1406 png_ptr
->transformations
&= ~PNG_ENCODE_ALPHA
;
1407 png_ptr
->flags
&= ~PNG_FLAG_OPTIMIZE_ALPHA
;
1411 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1412 /* Make sure the coefficients for the rgb to gray conversion are set
1415 if (png_ptr
->transformations
& PNG_RGB_TO_GRAY
)
1416 png_colorspace_set_rgb_coefficients(png_ptr
);
1419 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
1420 #if defined(PNG_READ_EXPAND_SUPPORTED) && defined(PNG_READ_BACKGROUND_SUPPORTED)
1421 /* Detect gray background and attempt to enable optimization for
1422 * gray --> RGB case.
1424 * Note: if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
1425 * RGB_ALPHA (in which case need_expand is superfluous anyway), the
1426 * background color might actually be gray yet not be flagged as such.
1427 * This is not a problem for the current code, which uses
1428 * PNG_BACKGROUND_IS_GRAY only to decide when to do the
1429 * png_do_gray_to_rgb() transformation.
1431 * TODO: this code needs to be revised to avoid the complexity and
1432 * interdependencies. The color type of the background should be recorded in
1433 * png_set_background, along with the bit depth, then the code has a record
1434 * of exactly what color space the background is currently in.
1436 if (png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
)
1438 /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
1439 * the file was grayscale the background value is gray.
1441 if (!(png_ptr
->color_type
& PNG_COLOR_MASK_COLOR
))
1442 png_ptr
->mode
|= PNG_BACKGROUND_IS_GRAY
;
1445 else if (png_ptr
->transformations
& PNG_COMPOSE
)
1447 /* PNG_COMPOSE: png_set_background was called with need_expand false,
1448 * so the color is in the color space of the output or png_set_alpha_mode
1449 * was called and the color is black. Ignore RGB_TO_GRAY because that
1450 * happens before GRAY_TO_RGB.
1452 if (png_ptr
->transformations
& PNG_GRAY_TO_RGB
)
1454 if (png_ptr
->background
.red
== png_ptr
->background
.green
&&
1455 png_ptr
->background
.red
== png_ptr
->background
.blue
)
1457 png_ptr
->mode
|= PNG_BACKGROUND_IS_GRAY
;
1458 png_ptr
->background
.gray
= png_ptr
->background
.red
;
1462 #endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
1463 #endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED */
1465 /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
1466 * can be performed directly on the palette, and some (such as rgb to gray)
1467 * can be optimized inside the palette. This is particularly true of the
1468 * composite (background and alpha) stuff, which can be pretty much all done
1469 * in the palette even if the result is expanded to RGB or gray afterward.
1471 * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
1472 * earlier and the palette stuff is actually handled on the first row. This
1473 * leads to the reported bug that the palette returned by png_get_PLTE is not
1476 if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
1477 png_init_palette_transformations(png_ptr
);
1480 png_init_rgb_transformations(png_ptr
);
1482 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1483 defined(PNG_READ_EXPAND_16_SUPPORTED)
1484 if ((png_ptr
->transformations
& PNG_EXPAND_16
) &&
1485 (png_ptr
->transformations
& PNG_COMPOSE
) &&
1486 !(png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) &&
1487 png_ptr
->bit_depth
!= 16)
1489 /* TODO: fix this. Because the expand_16 operation is after the compose
1490 * handling the background color must be 8, not 16, bits deep, but the
1491 * application will supply a 16-bit value so reduce it here.
1493 * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
1494 * present, so that case is ok (until do_expand_16 is moved.)
1496 * NOTE: this discards the low 16 bits of the user supplied background
1497 * color, but until expand_16 works properly there is no choice!
1499 # define CHOP(x) (x)=((png_uint_16)PNG_DIV257(x))
1500 CHOP(png_ptr
->background
.red
);
1501 CHOP(png_ptr
->background
.green
);
1502 CHOP(png_ptr
->background
.blue
);
1503 CHOP(png_ptr
->background
.gray
);
1506 #endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
1508 #if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
1509 (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
1510 defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
1511 if ((png_ptr
->transformations
& (PNG_16_TO_8
|PNG_SCALE_16_TO_8
)) &&
1512 (png_ptr
->transformations
& PNG_COMPOSE
) &&
1513 !(png_ptr
->transformations
& PNG_BACKGROUND_EXPAND
) &&
1514 png_ptr
->bit_depth
== 16)
1516 /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
1517 * component this will also happen after PNG_COMPOSE and so the background
1518 * color must be pre-expanded here.
1520 * TODO: fix this too.
1522 png_ptr
->background
.red
= (png_uint_16
)(png_ptr
->background
.red
* 257);
1523 png_ptr
->background
.green
=
1524 (png_uint_16
)(png_ptr
->background
.green
* 257);
1525 png_ptr
->background
.blue
= (png_uint_16
)(png_ptr
->background
.blue
* 257);
1526 png_ptr
->background
.gray
= (png_uint_16
)(png_ptr
->background
.gray
* 257);
1530 /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
1531 * background support (see the comments in scripts/pnglibconf.dfa), this
1532 * allows pre-multiplication of the alpha channel to be implemented as
1533 * compositing on black. This is probably sub-optimal and has been done in
1534 * 1.5.4 betas simply to enable external critique and testing (i.e. to
1535 * implement the new API quickly, without lots of internal changes.)
1538 #ifdef PNG_READ_GAMMA_SUPPORTED
1539 # ifdef PNG_READ_BACKGROUND_SUPPORTED
1540 /* Includes ALPHA_MODE */
1541 png_ptr
->background_1
= png_ptr
->background
;
1544 /* This needs to change - in the palette image case a whole set of tables are
1545 * built when it would be quicker to just calculate the correct value for
1546 * each palette entry directly. Also, the test is too tricky - why check
1547 * PNG_RGB_TO_GRAY if PNG_GAMMA is not set? The answer seems to be that
1548 * PNG_GAMMA is cancelled even if the gamma is known? The test excludes the
1549 * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
1550 * the gamma tables will not be built even if composition is required on a
1551 * gamma encoded value.
1553 * In 1.5.4 this is addressed below by an additional check on the individual
1554 * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
1557 if ((png_ptr
->transformations
& PNG_GAMMA
)
1558 || ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
)
1559 && (png_gamma_significant(png_ptr
->colorspace
.gamma
) ||
1560 png_gamma_significant(png_ptr
->screen_gamma
)))
1561 || ((png_ptr
->transformations
& PNG_COMPOSE
)
1562 && (png_gamma_significant(png_ptr
->colorspace
.gamma
)
1563 || png_gamma_significant(png_ptr
->screen_gamma
)
1564 # ifdef PNG_READ_BACKGROUND_SUPPORTED
1565 || (png_ptr
->background_gamma_type
== PNG_BACKGROUND_GAMMA_UNIQUE
1566 && png_gamma_significant(png_ptr
->background_gamma
))
1568 )) || ((png_ptr
->transformations
& PNG_ENCODE_ALPHA
)
1569 && png_gamma_significant(png_ptr
->screen_gamma
))
1572 png_build_gamma_table(png_ptr
, png_ptr
->bit_depth
);
1574 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1575 if (png_ptr
->transformations
& PNG_COMPOSE
)
1577 /* Issue a warning about this combination: because RGB_TO_GRAY is
1578 * optimized to do the gamma transform if present yet do_background has
1579 * to do the same thing if both options are set a
1580 * double-gamma-correction happens. This is true in all versions of
1583 if (png_ptr
->transformations
& PNG_RGB_TO_GRAY
)
1584 png_warning(png_ptr
,
1585 "libpng does not support gamma+background+rgb_to_gray");
1587 if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
1589 /* We don't get to here unless there is a tRNS chunk with non-opaque
1590 * entries - see the checking code at the start of this function.
1592 png_color back
, back_1
;
1593 png_colorp palette
= png_ptr
->palette
;
1594 int num_palette
= png_ptr
->num_palette
;
1596 if (png_ptr
->background_gamma_type
== PNG_BACKGROUND_GAMMA_FILE
)
1599 back
.red
= png_ptr
->gamma_table
[png_ptr
->background
.red
];
1600 back
.green
= png_ptr
->gamma_table
[png_ptr
->background
.green
];
1601 back
.blue
= png_ptr
->gamma_table
[png_ptr
->background
.blue
];
1603 back_1
.red
= png_ptr
->gamma_to_1
[png_ptr
->background
.red
];
1604 back_1
.green
= png_ptr
->gamma_to_1
[png_ptr
->background
.green
];
1605 back_1
.blue
= png_ptr
->gamma_to_1
[png_ptr
->background
.blue
];
1609 png_fixed_point g
, gs
;
1611 switch (png_ptr
->background_gamma_type
)
1613 case PNG_BACKGROUND_GAMMA_SCREEN
:
1614 g
= (png_ptr
->screen_gamma
);
1618 case PNG_BACKGROUND_GAMMA_FILE
:
1619 g
= png_reciprocal(png_ptr
->colorspace
.gamma
);
1620 gs
= png_reciprocal2(png_ptr
->colorspace
.gamma
,
1621 png_ptr
->screen_gamma
);
1624 case PNG_BACKGROUND_GAMMA_UNIQUE
:
1625 g
= png_reciprocal(png_ptr
->background_gamma
);
1626 gs
= png_reciprocal2(png_ptr
->background_gamma
,
1627 png_ptr
->screen_gamma
);
1630 g
= PNG_FP_1
; /* back_1 */
1631 gs
= PNG_FP_1
; /* back */
1635 if (png_gamma_significant(gs
))
1637 back
.red
= png_gamma_8bit_correct(png_ptr
->background
.red
,
1639 back
.green
= png_gamma_8bit_correct(png_ptr
->background
.green
,
1641 back
.blue
= png_gamma_8bit_correct(png_ptr
->background
.blue
,
1647 back
.red
= (png_byte
)png_ptr
->background
.red
;
1648 back
.green
= (png_byte
)png_ptr
->background
.green
;
1649 back
.blue
= (png_byte
)png_ptr
->background
.blue
;
1652 if (png_gamma_significant(g
))
1654 back_1
.red
= png_gamma_8bit_correct(png_ptr
->background
.red
,
1656 back_1
.green
= png_gamma_8bit_correct(
1657 png_ptr
->background
.green
, g
);
1658 back_1
.blue
= png_gamma_8bit_correct(png_ptr
->background
.blue
,
1664 back_1
.red
= (png_byte
)png_ptr
->background
.red
;
1665 back_1
.green
= (png_byte
)png_ptr
->background
.green
;
1666 back_1
.blue
= (png_byte
)png_ptr
->background
.blue
;
1670 for (i
= 0; i
< num_palette
; i
++)
1672 if (i
< (int)png_ptr
->num_trans
&&
1673 png_ptr
->trans_alpha
[i
] != 0xff)
1675 if (png_ptr
->trans_alpha
[i
] == 0)
1679 else /* if (png_ptr->trans_alpha[i] != 0xff) */
1683 v
= png_ptr
->gamma_to_1
[palette
[i
].red
];
1684 png_composite(w
, v
, png_ptr
->trans_alpha
[i
], back_1
.red
);
1685 palette
[i
].red
= png_ptr
->gamma_from_1
[w
];
1687 v
= png_ptr
->gamma_to_1
[palette
[i
].green
];
1688 png_composite(w
, v
, png_ptr
->trans_alpha
[i
], back_1
.green
);
1689 palette
[i
].green
= png_ptr
->gamma_from_1
[w
];
1691 v
= png_ptr
->gamma_to_1
[palette
[i
].blue
];
1692 png_composite(w
, v
, png_ptr
->trans_alpha
[i
], back_1
.blue
);
1693 palette
[i
].blue
= png_ptr
->gamma_from_1
[w
];
1698 palette
[i
].red
= png_ptr
->gamma_table
[palette
[i
].red
];
1699 palette
[i
].green
= png_ptr
->gamma_table
[palette
[i
].green
];
1700 palette
[i
].blue
= png_ptr
->gamma_table
[palette
[i
].blue
];
1704 /* Prevent the transformations being done again.
1706 * NOTE: this is highly dubious; it removes the transformations in
1707 * place. This seems inconsistent with the general treatment of the
1708 * transformations elsewhere.
1710 png_ptr
->transformations
&= ~(PNG_COMPOSE
| PNG_GAMMA
);
1711 } /* color_type == PNG_COLOR_TYPE_PALETTE */
1713 /* if (png_ptr->background_gamma_type!=PNG_BACKGROUND_GAMMA_UNKNOWN) */
1714 else /* color_type != PNG_COLOR_TYPE_PALETTE */
1717 png_fixed_point g
= PNG_FP_1
; /* Correction to linear */
1718 png_fixed_point gs
= PNG_FP_1
; /* Correction to screen */
1720 switch (png_ptr
->background_gamma_type
)
1722 case PNG_BACKGROUND_GAMMA_SCREEN
:
1723 g
= png_ptr
->screen_gamma
;
1724 /* gs = PNG_FP_1; */
1727 case PNG_BACKGROUND_GAMMA_FILE
:
1728 g
= png_reciprocal(png_ptr
->colorspace
.gamma
);
1729 gs
= png_reciprocal2(png_ptr
->colorspace
.gamma
,
1730 png_ptr
->screen_gamma
);
1733 case PNG_BACKGROUND_GAMMA_UNIQUE
:
1734 g
= png_reciprocal(png_ptr
->background_gamma
);
1735 gs
= png_reciprocal2(png_ptr
->background_gamma
,
1736 png_ptr
->screen_gamma
);
1740 png_error(png_ptr
, "invalid background gamma type");
1743 g_sig
= png_gamma_significant(g
);
1744 gs_sig
= png_gamma_significant(gs
);
1747 png_ptr
->background_1
.gray
= png_gamma_correct(png_ptr
,
1748 png_ptr
->background
.gray
, g
);
1751 png_ptr
->background
.gray
= png_gamma_correct(png_ptr
,
1752 png_ptr
->background
.gray
, gs
);
1754 if ((png_ptr
->background
.red
!= png_ptr
->background
.green
) ||
1755 (png_ptr
->background
.red
!= png_ptr
->background
.blue
) ||
1756 (png_ptr
->background
.red
!= png_ptr
->background
.gray
))
1758 /* RGB or RGBA with color background */
1761 png_ptr
->background_1
.red
= png_gamma_correct(png_ptr
,
1762 png_ptr
->background
.red
, g
);
1764 png_ptr
->background_1
.green
= png_gamma_correct(png_ptr
,
1765 png_ptr
->background
.green
, g
);
1767 png_ptr
->background_1
.blue
= png_gamma_correct(png_ptr
,
1768 png_ptr
->background
.blue
, g
);
1773 png_ptr
->background
.red
= png_gamma_correct(png_ptr
,
1774 png_ptr
->background
.red
, gs
);
1776 png_ptr
->background
.green
= png_gamma_correct(png_ptr
,
1777 png_ptr
->background
.green
, gs
);
1779 png_ptr
->background
.blue
= png_gamma_correct(png_ptr
,
1780 png_ptr
->background
.blue
, gs
);
1786 /* GRAY, GRAY ALPHA, RGB, or RGBA with gray background */
1787 png_ptr
->background_1
.red
= png_ptr
->background_1
.green
1788 = png_ptr
->background_1
.blue
= png_ptr
->background_1
.gray
;
1790 png_ptr
->background
.red
= png_ptr
->background
.green
1791 = png_ptr
->background
.blue
= png_ptr
->background
.gray
;
1794 /* The background is now in screen gamma: */
1795 png_ptr
->background_gamma_type
= PNG_BACKGROUND_GAMMA_SCREEN
;
1796 } /* color_type != PNG_COLOR_TYPE_PALETTE */
1797 }/* png_ptr->transformations & PNG_BACKGROUND */
1800 /* Transformation does not include PNG_BACKGROUND */
1801 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
1802 if (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
1803 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
1804 /* RGB_TO_GRAY needs to have non-gamma-corrected values! */
1805 && ((png_ptr
->transformations
& PNG_EXPAND
) == 0 ||
1806 (png_ptr
->transformations
& PNG_RGB_TO_GRAY
) == 0)
1810 png_colorp palette
= png_ptr
->palette
;
1811 int num_palette
= png_ptr
->num_palette
;
1814 /* NOTE: there are other transformations that should probably be in
1817 for (i
= 0; i
< num_palette
; i
++)
1819 palette
[i
].red
= png_ptr
->gamma_table
[palette
[i
].red
];
1820 palette
[i
].green
= png_ptr
->gamma_table
[palette
[i
].green
];
1821 palette
[i
].blue
= png_ptr
->gamma_table
[palette
[i
].blue
];
1824 /* Done the gamma correction. */
1825 png_ptr
->transformations
&= ~PNG_GAMMA
;
1826 } /* color_type == PALETTE && !PNG_BACKGROUND transformation */
1828 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1831 #endif /* PNG_READ_GAMMA_SUPPORTED */
1833 #ifdef PNG_READ_BACKGROUND_SUPPORTED
1834 /* No GAMMA transformation (see the hanging else 4 lines above) */
1835 if ((png_ptr
->transformations
& PNG_COMPOSE
) &&
1836 (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
))
1839 int istop
= (int)png_ptr
->num_trans
;
1841 png_colorp palette
= png_ptr
->palette
;
1843 back
.red
= (png_byte
)png_ptr
->background
.red
;
1844 back
.green
= (png_byte
)png_ptr
->background
.green
;
1845 back
.blue
= (png_byte
)png_ptr
->background
.blue
;
1847 for (i
= 0; i
< istop
; i
++)
1849 if (png_ptr
->trans_alpha
[i
] == 0)
1854 else if (png_ptr
->trans_alpha
[i
] != 0xff)
1856 /* The png_composite() macro is defined in png.h */
1857 png_composite(palette
[i
].red
, palette
[i
].red
,
1858 png_ptr
->trans_alpha
[i
], back
.red
);
1860 png_composite(palette
[i
].green
, palette
[i
].green
,
1861 png_ptr
->trans_alpha
[i
], back
.green
);
1863 png_composite(palette
[i
].blue
, palette
[i
].blue
,
1864 png_ptr
->trans_alpha
[i
], back
.blue
);
1868 png_ptr
->transformations
&= ~PNG_COMPOSE
;
1870 #endif /* PNG_READ_BACKGROUND_SUPPORTED */
1872 #ifdef PNG_READ_SHIFT_SUPPORTED
1873 if ((png_ptr
->transformations
& PNG_SHIFT
) &&
1874 !(png_ptr
->transformations
& PNG_EXPAND
) &&
1875 (png_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
))
1878 int istop
= png_ptr
->num_palette
;
1879 int shift
= 8 - png_ptr
->sig_bit
.red
;
1881 png_ptr
->transformations
&= ~PNG_SHIFT
;
1883 /* significant bits can be in the range 1 to 7 for a meaninful result, if
1884 * the number of significant bits is 0 then no shift is done (this is an
1885 * error condition which is silently ignored.)
1887 if (shift
> 0 && shift
< 8)
1888 for (i
=0; i
<istop
; ++i
)
1890 int component
= png_ptr
->palette
[i
].red
;
1892 component
>>= shift
;
1893 png_ptr
->palette
[i
].red
= (png_byte
)component
;
1896 shift
= 8 - png_ptr
->sig_bit
.green
;
1897 if (shift
> 0 && shift
< 8)
1898 for (i
=0; i
<istop
; ++i
)
1900 int component
= png_ptr
->palette
[i
].green
;
1902 component
>>= shift
;
1903 png_ptr
->palette
[i
].green
= (png_byte
)component
;
1906 shift
= 8 - png_ptr
->sig_bit
.blue
;
1907 if (shift
> 0 && shift
< 8)
1908 for (i
=0; i
<istop
; ++i
)
1910 int component
= png_ptr
->palette
[i
].blue
;
1912 component
>>= shift
;
1913 png_ptr
->palette
[i
].blue
= (png_byte
)component
;
1916 #endif /* PNG_READ_SHIFT_SUPPORTED */
1919 /* Modify the info structure to reflect the transformations. The
1920 * info should be updated so a PNG file could be written with it,
1921 * assuming the transformations result in valid PNG data.
1924 png_read_transform_info(png_structrp png_ptr
, png_inforp info_ptr
)
1926 png_debug(1, "in png_read_transform_info");
1928 #ifdef PNG_READ_EXPAND_SUPPORTED
1929 if (png_ptr
->transformations
& PNG_EXPAND
)
1931 if (info_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
1933 /* This check must match what actually happens in
1934 * png_do_expand_palette; if it ever checks the tRNS chunk to see if
1935 * it is all opaque we must do the same (at present it does not.)
1937 if (png_ptr
->num_trans
> 0)
1938 info_ptr
->color_type
= PNG_COLOR_TYPE_RGB_ALPHA
;
1941 info_ptr
->color_type
= PNG_COLOR_TYPE_RGB
;
1943 info_ptr
->bit_depth
= 8;
1944 info_ptr
->num_trans
= 0;
1946 if (png_ptr
->palette
== NULL
)
1947 png_error (png_ptr
, "Palette is NULL in indexed image");
1951 if (png_ptr
->num_trans
)
1953 if (png_ptr
->transformations
& PNG_EXPAND_tRNS
)
1954 info_ptr
->color_type
|= PNG_COLOR_MASK_ALPHA
;
1956 if (info_ptr
->bit_depth
< 8)
1957 info_ptr
->bit_depth
= 8;
1959 info_ptr
->num_trans
= 0;
1964 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
1965 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
1966 /* The following is almost certainly wrong unless the background value is in
1969 if (png_ptr
->transformations
& PNG_COMPOSE
)
1970 info_ptr
->background
= png_ptr
->background
;
1973 #ifdef PNG_READ_GAMMA_SUPPORTED
1974 /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
1975 * however it seems that the code in png_init_read_transformations, which has
1976 * been called before this from png_read_update_info->png_read_start_row
1977 * sometimes does the gamma transform and cancels the flag.
1979 * TODO: this looks wrong; the info_ptr should end up with a gamma equal to
1980 * the screen_gamma value. The following probably results in weirdness if
1981 * the info_ptr is used by the app after the rows have been read.
1983 info_ptr
->colorspace
.gamma
= png_ptr
->colorspace
.gamma
;
1986 if (info_ptr
->bit_depth
== 16)
1988 # ifdef PNG_READ_16BIT_SUPPORTED
1989 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
1990 if (png_ptr
->transformations
& PNG_SCALE_16_TO_8
)
1991 info_ptr
->bit_depth
= 8;
1994 # ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
1995 if (png_ptr
->transformations
& PNG_16_TO_8
)
1996 info_ptr
->bit_depth
= 8;
2000 /* No 16 bit support: force chopping 16-bit input down to 8, in this case
2001 * the app program can chose if both APIs are available by setting the
2002 * correct scaling to use.
2004 # ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2005 /* For compatibility with previous versions use the strip method by
2006 * default. This code works because if PNG_SCALE_16_TO_8 is already
2007 * set the code below will do that in preference to the chop.
2009 png_ptr
->transformations
|= PNG_16_TO_8
;
2010 info_ptr
->bit_depth
= 8;
2013 # ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2014 png_ptr
->transformations
|= PNG_SCALE_16_TO_8
;
2015 info_ptr
->bit_depth
= 8;
2018 CONFIGURATION ERROR
: you must enable at least one
16 to
8 method
2021 #endif /* !READ_16BIT_SUPPORTED */
2024 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2025 if (png_ptr
->transformations
& PNG_GRAY_TO_RGB
)
2026 info_ptr
->color_type
= (png_byte
)(info_ptr
->color_type
|
2027 PNG_COLOR_MASK_COLOR
);
2030 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2031 if (png_ptr
->transformations
& PNG_RGB_TO_GRAY
)
2032 info_ptr
->color_type
= (png_byte
)(info_ptr
->color_type
&
2033 ~PNG_COLOR_MASK_COLOR
);
2036 #ifdef PNG_READ_QUANTIZE_SUPPORTED
2037 if (png_ptr
->transformations
& PNG_QUANTIZE
)
2039 if (((info_ptr
->color_type
== PNG_COLOR_TYPE_RGB
) ||
2040 (info_ptr
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)) &&
2041 png_ptr
->palette_lookup
&& info_ptr
->bit_depth
== 8)
2043 info_ptr
->color_type
= PNG_COLOR_TYPE_PALETTE
;
2048 #ifdef PNG_READ_EXPAND_16_SUPPORTED
2049 if (png_ptr
->transformations
& PNG_EXPAND_16
&& info_ptr
->bit_depth
== 8 &&
2050 info_ptr
->color_type
!= PNG_COLOR_TYPE_PALETTE
)
2052 info_ptr
->bit_depth
= 16;
2056 #ifdef PNG_READ_PACK_SUPPORTED
2057 if ((png_ptr
->transformations
& PNG_PACK
) && (info_ptr
->bit_depth
< 8))
2058 info_ptr
->bit_depth
= 8;
2061 if (info_ptr
->color_type
== PNG_COLOR_TYPE_PALETTE
)
2062 info_ptr
->channels
= 1;
2064 else if (info_ptr
->color_type
& PNG_COLOR_MASK_COLOR
)
2065 info_ptr
->channels
= 3;
2068 info_ptr
->channels
= 1;
2070 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
2071 if (png_ptr
->transformations
& PNG_STRIP_ALPHA
)
2073 info_ptr
->color_type
= (png_byte
)(info_ptr
->color_type
&
2074 ~PNG_COLOR_MASK_ALPHA
);
2075 info_ptr
->num_trans
= 0;
2079 if (info_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
)
2080 info_ptr
->channels
++;
2082 #ifdef PNG_READ_FILLER_SUPPORTED
2083 /* STRIP_ALPHA and FILLER allowed: MASK_ALPHA bit stripped above */
2084 if ((png_ptr
->transformations
& PNG_FILLER
) &&
2085 ((info_ptr
->color_type
== PNG_COLOR_TYPE_RGB
) ||
2086 (info_ptr
->color_type
== PNG_COLOR_TYPE_GRAY
)))
2088 info_ptr
->channels
++;
2089 /* If adding a true alpha channel not just filler */
2090 if (png_ptr
->transformations
& PNG_ADD_ALPHA
)
2091 info_ptr
->color_type
|= PNG_COLOR_MASK_ALPHA
;
2095 #if defined(PNG_USER_TRANSFORM_PTR_SUPPORTED) && \
2096 defined(PNG_READ_USER_TRANSFORM_SUPPORTED)
2097 if (png_ptr
->transformations
& PNG_USER_TRANSFORM
)
2099 if (info_ptr
->bit_depth
< png_ptr
->user_transform_depth
)
2100 info_ptr
->bit_depth
= png_ptr
->user_transform_depth
;
2102 if (info_ptr
->channels
< png_ptr
->user_transform_channels
)
2103 info_ptr
->channels
= png_ptr
->user_transform_channels
;
2107 info_ptr
->pixel_depth
= (png_byte
)(info_ptr
->channels
*
2108 info_ptr
->bit_depth
);
2110 info_ptr
->rowbytes
= PNG_ROWBYTES(info_ptr
->pixel_depth
, info_ptr
->width
);
2112 /* Adding in 1.5.4: cache the above value in png_struct so that we can later
2113 * check in png_rowbytes that the user buffer won't get overwritten. Note
2114 * that the field is not always set - if png_read_update_info isn't called
2115 * the application has to either not do any transforms or get the calculation
2118 png_ptr
->info_rowbytes
= info_ptr
->rowbytes
;
2120 #ifndef PNG_READ_EXPAND_SUPPORTED
2126 #ifdef PNG_READ_PACK_SUPPORTED
2127 /* Unpack pixels of 1, 2, or 4 bits per pixel into 1 byte per pixel,
2128 * without changing the actual values. Thus, if you had a row with
2129 * a bit depth of 1, you would end up with bytes that only contained
2130 * the numbers 0 or 1. If you would rather they contain 0 and 255, use
2131 * png_do_shift() after this.
2134 png_do_unpack(png_row_infop row_info
, png_bytep row
)
2136 png_debug(1, "in png_do_unpack");
2138 if (row_info
->bit_depth
< 8)
2141 png_uint_32 row_width
=row_info
->width
;
2143 switch (row_info
->bit_depth
)
2147 png_bytep sp
= row
+ (png_size_t
)((row_width
- 1) >> 3);
2148 png_bytep dp
= row
+ (png_size_t
)row_width
- 1;
2149 png_uint_32 shift
= 7 - (int)((row_width
+ 7) & 0x07);
2150 for (i
= 0; i
< row_width
; i
++)
2152 *dp
= (png_byte
)((*sp
>> shift
) & 0x01);
2171 png_bytep sp
= row
+ (png_size_t
)((row_width
- 1) >> 2);
2172 png_bytep dp
= row
+ (png_size_t
)row_width
- 1;
2173 png_uint_32 shift
= (int)((3 - ((row_width
+ 3) & 0x03)) << 1);
2174 for (i
= 0; i
< row_width
; i
++)
2176 *dp
= (png_byte
)((*sp
>> shift
) & 0x03);
2194 png_bytep sp
= row
+ (png_size_t
)((row_width
- 1) >> 1);
2195 png_bytep dp
= row
+ (png_size_t
)row_width
- 1;
2196 png_uint_32 shift
= (int)((1 - ((row_width
+ 1) & 0x01)) << 2);
2197 for (i
= 0; i
< row_width
; i
++)
2199 *dp
= (png_byte
)((*sp
>> shift
) & 0x0f);
2218 row_info
->bit_depth
= 8;
2219 row_info
->pixel_depth
= (png_byte
)(8 * row_info
->channels
);
2220 row_info
->rowbytes
= row_width
* row_info
->channels
;
2225 #ifdef PNG_READ_SHIFT_SUPPORTED
2226 /* Reverse the effects of png_do_shift. This routine merely shifts the
2227 * pixels back to their significant bits values. Thus, if you have
2228 * a row of bit depth 8, but only 5 are significant, this will shift
2229 * the values back to 0 through 31.
2232 png_do_unshift(png_row_infop row_info
, png_bytep row
,
2233 png_const_color_8p sig_bits
)
2237 png_debug(1, "in png_do_unshift");
2239 /* The palette case has already been handled in the _init routine. */
2240 color_type
= row_info
->color_type
;
2242 if (color_type
!= PNG_COLOR_TYPE_PALETTE
)
2246 int bit_depth
= row_info
->bit_depth
;
2248 if (color_type
& PNG_COLOR_MASK_COLOR
)
2250 shift
[channels
++] = bit_depth
- sig_bits
->red
;
2251 shift
[channels
++] = bit_depth
- sig_bits
->green
;
2252 shift
[channels
++] = bit_depth
- sig_bits
->blue
;
2257 shift
[channels
++] = bit_depth
- sig_bits
->gray
;
2260 if (color_type
& PNG_COLOR_MASK_ALPHA
)
2262 shift
[channels
++] = bit_depth
- sig_bits
->alpha
;
2268 for (c
= have_shift
= 0; c
< channels
; ++c
)
2270 /* A shift of more than the bit depth is an error condition but it
2271 * gets ignored here.
2273 if (shift
[c
] <= 0 || shift
[c
] >= bit_depth
)
2287 /* Must be 1bpp gray: should not be here! */
2292 /* Must be 2bpp gray */
2293 /* assert(channels == 1 && shift[0] == 1) */
2296 png_bytep bp_end
= bp
+ row_info
->rowbytes
;
2300 int b
= (*bp
>> 1) & 0x55;
2301 *bp
++ = (png_byte
)b
;
2307 /* Must be 4bpp gray */
2308 /* assert(channels == 1) */
2311 png_bytep bp_end
= bp
+ row_info
->rowbytes
;
2312 int gray_shift
= shift
[0];
2313 int mask
= 0xf >> gray_shift
;
2319 int b
= (*bp
>> gray_shift
) & mask
;
2320 *bp
++ = (png_byte
)b
;
2326 /* Single byte components, G, GA, RGB, RGBA */
2329 png_bytep bp_end
= bp
+ row_info
->rowbytes
;
2334 int b
= *bp
>> shift
[channel
];
2335 if (++channel
>= channels
)
2337 *bp
++ = (png_byte
)b
;
2342 #ifdef PNG_READ_16BIT_SUPPORTED
2344 /* Double byte components, G, GA, RGB, RGBA */
2347 png_bytep bp_end
= bp
+ row_info
->rowbytes
;
2352 int value
= (bp
[0] << 8) + bp
[1];
2354 value
>>= shift
[channel
];
2355 if (++channel
>= channels
)
2357 *bp
++ = (png_byte
)(value
>> 8);
2358 *bp
++ = (png_byte
)(value
& 0xff);
2368 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
2369 /* Scale rows of bit depth 16 down to 8 accurately */
2371 png_do_scale_16_to_8(png_row_infop row_info
, png_bytep row
)
2373 png_debug(1, "in png_do_scale_16_to_8");
2375 if (row_info
->bit_depth
== 16)
2377 png_bytep sp
= row
; /* source */
2378 png_bytep dp
= row
; /* destination */
2379 png_bytep ep
= sp
+ row_info
->rowbytes
; /* end+1 */
2383 /* The input is an array of 16 bit components, these must be scaled to
2384 * 8 bits each. For a 16 bit value V the required value (from the PNG
2385 * specification) is:
2389 * This reduces to round(V / 257), or floor((V + 128.5)/257)
2391 * Represent V as the two byte value vhi.vlo. Make a guess that the
2392 * result is the top byte of V, vhi, then the correction to this value
2395 * error = floor(((V-vhi.vhi) + 128.5) / 257)
2396 * = floor(((vlo-vhi) + 128.5) / 257)
2398 * This can be approximated using integer arithmetic (and a signed
2401 * error = (vlo-vhi+128) >> 8;
2403 * The approximate differs from the exact answer only when (vlo-vhi) is
2404 * 128; it then gives a correction of +1 when the exact correction is
2405 * 0. This gives 128 errors. The exact answer (correct for all 16 bit
2408 * error = (vlo-vhi+128)*65535 >> 24;
2410 * An alternative arithmetic calculation which also gives no errors is:
2412 * (V * 255 + 32895) >> 16
2415 png_int_32 tmp
= *sp
++; /* must be signed! */
2416 tmp
+= (((int)*sp
++ - tmp
+ 128) * 65535) >> 24;
2417 *dp
++ = (png_byte
)tmp
;
2420 row_info
->bit_depth
= 8;
2421 row_info
->pixel_depth
= (png_byte
)(8 * row_info
->channels
);
2422 row_info
->rowbytes
= row_info
->width
* row_info
->channels
;
2427 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
2429 /* Simply discard the low byte. This was the default behavior prior
2432 png_do_chop(png_row_infop row_info
, png_bytep row
)
2434 png_debug(1, "in png_do_chop");
2436 if (row_info
->bit_depth
== 16)
2438 png_bytep sp
= row
; /* source */
2439 png_bytep dp
= row
; /* destination */
2440 png_bytep ep
= sp
+ row_info
->rowbytes
; /* end+1 */
2445 sp
+= 2; /* skip low byte */
2448 row_info
->bit_depth
= 8;
2449 row_info
->pixel_depth
= (png_byte
)(8 * row_info
->channels
);
2450 row_info
->rowbytes
= row_info
->width
* row_info
->channels
;
2455 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
2457 png_do_read_swap_alpha(png_row_infop row_info
, png_bytep row
)
2459 png_debug(1, "in png_do_read_swap_alpha");
2462 png_uint_32 row_width
= row_info
->width
;
2463 if (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)
2465 /* This converts from RGBA to ARGB */
2466 if (row_info
->bit_depth
== 8)
2468 png_bytep sp
= row
+ row_info
->rowbytes
;
2473 for (i
= 0; i
< row_width
; i
++)
2483 #ifdef PNG_READ_16BIT_SUPPORTED
2484 /* This converts from RRGGBBAA to AARRGGBB */
2487 png_bytep sp
= row
+ row_info
->rowbytes
;
2492 for (i
= 0; i
< row_width
; i
++)
2509 else if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
)
2511 /* This converts from GA to AG */
2512 if (row_info
->bit_depth
== 8)
2514 png_bytep sp
= row
+ row_info
->rowbytes
;
2519 for (i
= 0; i
< row_width
; i
++)
2527 #ifdef PNG_READ_16BIT_SUPPORTED
2528 /* This converts from GGAA to AAGG */
2531 png_bytep sp
= row
+ row_info
->rowbytes
;
2536 for (i
= 0; i
< row_width
; i
++)
2552 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
2554 png_do_read_invert_alpha(png_row_infop row_info
, png_bytep row
)
2556 png_uint_32 row_width
;
2557 png_debug(1, "in png_do_read_invert_alpha");
2559 row_width
= row_info
->width
;
2560 if (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
)
2562 if (row_info
->bit_depth
== 8)
2564 /* This inverts the alpha channel in RGBA */
2565 png_bytep sp
= row
+ row_info
->rowbytes
;
2569 for (i
= 0; i
< row_width
; i
++)
2571 *(--dp
) = (png_byte
)(255 - *(--sp
));
2573 /* This does nothing:
2577 We can replace it with:
2584 #ifdef PNG_READ_16BIT_SUPPORTED
2585 /* This inverts the alpha channel in RRGGBBAA */
2588 png_bytep sp
= row
+ row_info
->rowbytes
;
2592 for (i
= 0; i
< row_width
; i
++)
2594 *(--dp
) = (png_byte
)(255 - *(--sp
));
2595 *(--dp
) = (png_byte
)(255 - *(--sp
));
2597 /* This does nothing:
2604 We can replace it with:
2612 else if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
)
2614 if (row_info
->bit_depth
== 8)
2616 /* This inverts the alpha channel in GA */
2617 png_bytep sp
= row
+ row_info
->rowbytes
;
2621 for (i
= 0; i
< row_width
; i
++)
2623 *(--dp
) = (png_byte
)(255 - *(--sp
));
2628 #ifdef PNG_READ_16BIT_SUPPORTED
2631 /* This inverts the alpha channel in GGAA */
2632 png_bytep sp
= row
+ row_info
->rowbytes
;
2636 for (i
= 0; i
< row_width
; i
++)
2638 *(--dp
) = (png_byte
)(255 - *(--sp
));
2639 *(--dp
) = (png_byte
)(255 - *(--sp
));
2653 #ifdef PNG_READ_FILLER_SUPPORTED
2654 /* Add filler channel if we have RGB color */
2656 png_do_read_filler(png_row_infop row_info
, png_bytep row
,
2657 png_uint_32 filler
, png_uint_32 flags
)
2660 png_uint_32 row_width
= row_info
->width
;
2662 #ifdef PNG_READ_16BIT_SUPPORTED
2663 png_byte hi_filler
= (png_byte
)((filler
>>8) & 0xff);
2665 png_byte lo_filler
= (png_byte
)(filler
& 0xff);
2667 png_debug(1, "in png_do_read_filler");
2670 row_info
->color_type
== PNG_COLOR_TYPE_GRAY
)
2672 if (row_info
->bit_depth
== 8)
2674 if (flags
& PNG_FLAG_FILLER_AFTER
)
2676 /* This changes the data from G to GX */
2677 png_bytep sp
= row
+ (png_size_t
)row_width
;
2678 png_bytep dp
= sp
+ (png_size_t
)row_width
;
2679 for (i
= 1; i
< row_width
; i
++)
2681 *(--dp
) = lo_filler
;
2684 *(--dp
) = lo_filler
;
2685 row_info
->channels
= 2;
2686 row_info
->pixel_depth
= 16;
2687 row_info
->rowbytes
= row_width
* 2;
2692 /* This changes the data from G to XG */
2693 png_bytep sp
= row
+ (png_size_t
)row_width
;
2694 png_bytep dp
= sp
+ (png_size_t
)row_width
;
2695 for (i
= 0; i
< row_width
; i
++)
2698 *(--dp
) = lo_filler
;
2700 row_info
->channels
= 2;
2701 row_info
->pixel_depth
= 16;
2702 row_info
->rowbytes
= row_width
* 2;
2706 #ifdef PNG_READ_16BIT_SUPPORTED
2707 else if (row_info
->bit_depth
== 16)
2709 if (flags
& PNG_FLAG_FILLER_AFTER
)
2711 /* This changes the data from GG to GGXX */
2712 png_bytep sp
= row
+ (png_size_t
)row_width
* 2;
2713 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2714 for (i
= 1; i
< row_width
; i
++)
2716 *(--dp
) = hi_filler
;
2717 *(--dp
) = lo_filler
;
2721 *(--dp
) = hi_filler
;
2722 *(--dp
) = lo_filler
;
2723 row_info
->channels
= 2;
2724 row_info
->pixel_depth
= 32;
2725 row_info
->rowbytes
= row_width
* 4;
2730 /* This changes the data from GG to XXGG */
2731 png_bytep sp
= row
+ (png_size_t
)row_width
* 2;
2732 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2733 for (i
= 0; i
< row_width
; i
++)
2737 *(--dp
) = hi_filler
;
2738 *(--dp
) = lo_filler
;
2740 row_info
->channels
= 2;
2741 row_info
->pixel_depth
= 32;
2742 row_info
->rowbytes
= row_width
* 4;
2746 } /* COLOR_TYPE == GRAY */
2747 else if (row_info
->color_type
== PNG_COLOR_TYPE_RGB
)
2749 if (row_info
->bit_depth
== 8)
2751 if (flags
& PNG_FLAG_FILLER_AFTER
)
2753 /* This changes the data from RGB to RGBX */
2754 png_bytep sp
= row
+ (png_size_t
)row_width
* 3;
2755 png_bytep dp
= sp
+ (png_size_t
)row_width
;
2756 for (i
= 1; i
< row_width
; i
++)
2758 *(--dp
) = lo_filler
;
2763 *(--dp
) = lo_filler
;
2764 row_info
->channels
= 4;
2765 row_info
->pixel_depth
= 32;
2766 row_info
->rowbytes
= row_width
* 4;
2771 /* This changes the data from RGB to XRGB */
2772 png_bytep sp
= row
+ (png_size_t
)row_width
* 3;
2773 png_bytep dp
= sp
+ (png_size_t
)row_width
;
2774 for (i
= 0; i
< row_width
; i
++)
2779 *(--dp
) = lo_filler
;
2781 row_info
->channels
= 4;
2782 row_info
->pixel_depth
= 32;
2783 row_info
->rowbytes
= row_width
* 4;
2787 #ifdef PNG_READ_16BIT_SUPPORTED
2788 else if (row_info
->bit_depth
== 16)
2790 if (flags
& PNG_FLAG_FILLER_AFTER
)
2792 /* This changes the data from RRGGBB to RRGGBBXX */
2793 png_bytep sp
= row
+ (png_size_t
)row_width
* 6;
2794 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2795 for (i
= 1; i
< row_width
; i
++)
2797 *(--dp
) = hi_filler
;
2798 *(--dp
) = lo_filler
;
2806 *(--dp
) = hi_filler
;
2807 *(--dp
) = lo_filler
;
2808 row_info
->channels
= 4;
2809 row_info
->pixel_depth
= 64;
2810 row_info
->rowbytes
= row_width
* 8;
2815 /* This changes the data from RRGGBB to XXRRGGBB */
2816 png_bytep sp
= row
+ (png_size_t
)row_width
* 6;
2817 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2818 for (i
= 0; i
< row_width
; i
++)
2826 *(--dp
) = hi_filler
;
2827 *(--dp
) = lo_filler
;
2830 row_info
->channels
= 4;
2831 row_info
->pixel_depth
= 64;
2832 row_info
->rowbytes
= row_width
* 8;
2836 } /* COLOR_TYPE == RGB */
2840 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
2841 /* Expand grayscale files to RGB, with or without alpha */
2843 png_do_gray_to_rgb(png_row_infop row_info
, png_bytep row
)
2846 png_uint_32 row_width
= row_info
->width
;
2848 png_debug(1, "in png_do_gray_to_rgb");
2850 if (row_info
->bit_depth
>= 8 &&
2851 !(row_info
->color_type
& PNG_COLOR_MASK_COLOR
))
2853 if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY
)
2855 if (row_info
->bit_depth
== 8)
2857 /* This changes G to RGB */
2858 png_bytep sp
= row
+ (png_size_t
)row_width
- 1;
2859 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2860 for (i
= 0; i
< row_width
; i
++)
2870 /* This changes GG to RRGGBB */
2871 png_bytep sp
= row
+ (png_size_t
)row_width
* 2 - 1;
2872 png_bytep dp
= sp
+ (png_size_t
)row_width
* 4;
2873 for (i
= 0; i
< row_width
; i
++)
2876 *(dp
--) = *(sp
- 1);
2878 *(dp
--) = *(sp
- 1);
2885 else if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
)
2887 if (row_info
->bit_depth
== 8)
2889 /* This changes GA to RGBA */
2890 png_bytep sp
= row
+ (png_size_t
)row_width
* 2 - 1;
2891 png_bytep dp
= sp
+ (png_size_t
)row_width
* 2;
2892 for (i
= 0; i
< row_width
; i
++)
2903 /* This changes GGAA to RRGGBBAA */
2904 png_bytep sp
= row
+ (png_size_t
)row_width
* 4 - 1;
2905 png_bytep dp
= sp
+ (png_size_t
)row_width
* 4;
2906 for (i
= 0; i
< row_width
; i
++)
2911 *(dp
--) = *(sp
- 1);
2913 *(dp
--) = *(sp
- 1);
2919 row_info
->channels
= (png_byte
)(row_info
->channels
+ 2);
2920 row_info
->color_type
|= PNG_COLOR_MASK_COLOR
;
2921 row_info
->pixel_depth
= (png_byte
)(row_info
->channels
*
2922 row_info
->bit_depth
);
2923 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
2928 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
2929 /* Reduce RGB files to grayscale, with or without alpha
2930 * using the equation given in Poynton's ColorFAQ of 1998-01-04 at
2931 * <http://www.inforamp.net/~poynton/> (THIS LINK IS DEAD June 2008 but
2932 * versions dated 1998 through November 2002 have been archived at
2933 * http://web.archive.org/web/20000816232553/http://www.inforamp.net/
2934 * ~poynton/notes/colour_and_gamma/ColorFAQ.txt )
2935 * Charles Poynton poynton at poynton.com
2937 * Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
2939 * which can be expressed with integers as
2941 * Y = (6969 * R + 23434 * G + 2365 * B)/32768
2943 * Poynton's current link (as of January 2003 through July 2011):
2944 * <http://www.poynton.com/notes/colour_and_gamma/>
2945 * has changed the numbers slightly:
2947 * Y = 0.2126*R + 0.7152*G + 0.0722*B
2949 * which can be expressed with integers as
2951 * Y = (6966 * R + 23436 * G + 2366 * B)/32768
2953 * Historically, however, libpng uses numbers derived from the ITU-R Rec 709
2954 * end point chromaticities and the D65 white point. Depending on the
2955 * precision used for the D65 white point this produces a variety of different
2956 * numbers, however if the four decimal place value used in ITU-R Rec 709 is
2957 * used (0.3127,0.3290) the Y calculation would be:
2959 * Y = (6968 * R + 23435 * G + 2366 * B)/32768
2961 * While this is correct the rounding results in an overflow for white, because
2962 * the sum of the rounded coefficients is 32769, not 32768. Consequently
2963 * libpng uses, instead, the closest non-overflowing approximation:
2965 * Y = (6968 * R + 23434 * G + 2366 * B)/32768
2967 * Starting with libpng-1.5.5, if the image being converted has a cHRM chunk
2968 * (including an sRGB chunk) then the chromaticities are used to calculate the
2969 * coefficients. See the chunk handling in pngrutil.c for more information.
2971 * In all cases the calculation is to be done in a linear colorspace. If no
2972 * gamma information is available to correct the encoding of the original RGB
2973 * values this results in an implicit assumption that the original PNG RGB
2974 * values were linear.
2976 * Other integer coefficents can be used via png_set_rgb_to_gray(). Because
2977 * the API takes just red and green coefficients the blue coefficient is
2978 * calculated to make the sum 32768. This will result in different rounding
2979 * to that used above.
2982 png_do_rgb_to_gray(png_structrp png_ptr
, png_row_infop row_info
, png_bytep row
)
2987 png_debug(1, "in png_do_rgb_to_gray");
2989 if (!(row_info
->color_type
& PNG_COLOR_MASK_PALETTE
) &&
2990 (row_info
->color_type
& PNG_COLOR_MASK_COLOR
))
2992 PNG_CONST png_uint_32 rc
= png_ptr
->rgb_to_gray_red_coeff
;
2993 PNG_CONST png_uint_32 gc
= png_ptr
->rgb_to_gray_green_coeff
;
2994 PNG_CONST png_uint_32 bc
= 32768 - rc
- gc
;
2995 PNG_CONST png_uint_32 row_width
= row_info
->width
;
2996 PNG_CONST
int have_alpha
=
2997 (row_info
->color_type
& PNG_COLOR_MASK_ALPHA
) != 0;
2999 if (row_info
->bit_depth
== 8)
3001 #ifdef PNG_READ_GAMMA_SUPPORTED
3002 /* Notice that gamma to/from 1 are not necessarily inverses (if
3003 * there is an overall gamma correction). Prior to 1.5.5 this code
3004 * checked the linearized values for equality; this doesn't match
3005 * the documentation, the original values must be checked.
3007 if (png_ptr
->gamma_from_1
!= NULL
&& png_ptr
->gamma_to_1
!= NULL
)
3013 for (i
= 0; i
< row_width
; i
++)
3015 png_byte red
= *(sp
++);
3016 png_byte green
= *(sp
++);
3017 png_byte blue
= *(sp
++);
3019 if (red
!= green
|| red
!= blue
)
3021 red
= png_ptr
->gamma_to_1
[red
];
3022 green
= png_ptr
->gamma_to_1
[green
];
3023 blue
= png_ptr
->gamma_to_1
[blue
];
3026 *(dp
++) = png_ptr
->gamma_from_1
[
3027 (rc
*red
+ gc
*green
+ bc
*blue
+ 16384)>>15];
3032 /* If there is no overall correction the table will not be
3035 if (png_ptr
->gamma_table
!= NULL
)
3036 red
= png_ptr
->gamma_table
[red
];
3052 for (i
= 0; i
< row_width
; i
++)
3054 png_byte red
= *(sp
++);
3055 png_byte green
= *(sp
++);
3056 png_byte blue
= *(sp
++);
3058 if (red
!= green
|| red
!= blue
)
3061 /* NOTE: this is the historical approach which simply
3062 * truncates the results.
3064 *(dp
++) = (png_byte
)((rc
*red
+ gc
*green
+ bc
*blue
)>>15);
3076 else /* RGB bit_depth == 16 */
3078 #ifdef PNG_READ_GAMMA_SUPPORTED
3079 if (png_ptr
->gamma_16_to_1
!= NULL
&& png_ptr
->gamma_16_from_1
!= NULL
)
3085 for (i
= 0; i
< row_width
; i
++)
3087 png_uint_16 red
, green
, blue
, w
;
3089 red
= (png_uint_16
)(((*(sp
))<<8) | *(sp
+ 1)); sp
+= 2;
3090 green
= (png_uint_16
)(((*(sp
))<<8) | *(sp
+ 1)); sp
+= 2;
3091 blue
= (png_uint_16
)(((*(sp
))<<8) | *(sp
+ 1)); sp
+= 2;
3093 if (red
== green
&& red
== blue
)
3095 if (png_ptr
->gamma_16_table
!= NULL
)
3096 w
= png_ptr
->gamma_16_table
[(red
&0xff)
3097 >> png_ptr
->gamma_shift
][red
>>8];
3105 png_uint_16 red_1
= png_ptr
->gamma_16_to_1
[(red
&0xff)
3106 >> png_ptr
->gamma_shift
][red
>>8];
3107 png_uint_16 green_1
=
3108 png_ptr
->gamma_16_to_1
[(green
&0xff) >>
3109 png_ptr
->gamma_shift
][green
>>8];
3110 png_uint_16 blue_1
= png_ptr
->gamma_16_to_1
[(blue
&0xff)
3111 >> png_ptr
->gamma_shift
][blue
>>8];
3112 png_uint_16 gray16
= (png_uint_16
)((rc
*red_1
+ gc
*green_1
3113 + bc
*blue_1
+ 16384)>>15);
3114 w
= png_ptr
->gamma_16_from_1
[(gray16
&0xff) >>
3115 png_ptr
->gamma_shift
][gray16
>> 8];
3119 *(dp
++) = (png_byte
)((w
>>8) & 0xff);
3120 *(dp
++) = (png_byte
)(w
& 0xff);
3136 for (i
= 0; i
< row_width
; i
++)
3138 png_uint_16 red
, green
, blue
, gray16
;
3140 red
= (png_uint_16
)(((*(sp
))<<8) | *(sp
+ 1)); sp
+= 2;
3141 green
= (png_uint_16
)(((*(sp
))<<8) | *(sp
+ 1)); sp
+= 2;
3142 blue
= (png_uint_16
)(((*(sp
))<<8) | *(sp
+ 1)); sp
+= 2;
3144 if (red
!= green
|| red
!= blue
)
3147 /* From 1.5.5 in the 16 bit case do the accurate conversion even
3148 * in the 'fast' case - this is because this is where the code
3149 * ends up when handling linear 16 bit data.
3151 gray16
= (png_uint_16
)((rc
*red
+ gc
*green
+ bc
*blue
+ 16384) >>
3153 *(dp
++) = (png_byte
)((gray16
>>8) & 0xff);
3154 *(dp
++) = (png_byte
)(gray16
& 0xff);
3165 row_info
->channels
= (png_byte
)(row_info
->channels
- 2);
3166 row_info
->color_type
= (png_byte
)(row_info
->color_type
&
3167 ~PNG_COLOR_MASK_COLOR
);
3168 row_info
->pixel_depth
= (png_byte
)(row_info
->channels
*
3169 row_info
->bit_depth
);
3170 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
3176 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
3177 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
3178 /* Replace any alpha or transparency with the supplied background color.
3179 * "background" is already in the screen gamma, while "background_1" is
3180 * at a gamma of 1.0. Paletted files have already been taken care of.
3183 png_do_compose(png_row_infop row_info
, png_bytep row
, png_structrp png_ptr
)
3185 #ifdef PNG_READ_GAMMA_SUPPORTED
3186 png_const_bytep gamma_table
= png_ptr
->gamma_table
;
3187 png_const_bytep gamma_from_1
= png_ptr
->gamma_from_1
;
3188 png_const_bytep gamma_to_1
= png_ptr
->gamma_to_1
;
3189 png_const_uint_16pp gamma_16
= png_ptr
->gamma_16_table
;
3190 png_const_uint_16pp gamma_16_from_1
= png_ptr
->gamma_16_from_1
;
3191 png_const_uint_16pp gamma_16_to_1
= png_ptr
->gamma_16_to_1
;
3192 int gamma_shift
= png_ptr
->gamma_shift
;
3193 int optimize
= (png_ptr
->flags
& PNG_FLAG_OPTIMIZE_ALPHA
) != 0;
3198 png_uint_32 row_width
= row_info
->width
;
3201 png_debug(1, "in png_do_compose");
3204 switch (row_info
->color_type
)
3206 case PNG_COLOR_TYPE_GRAY
:
3208 switch (row_info
->bit_depth
)
3214 for (i
= 0; i
< row_width
; i
++)
3216 if ((png_uint_16
)((*sp
>> shift
) & 0x01)
3217 == png_ptr
->trans_color
.gray
)
3219 unsigned int tmp
= *sp
& (0x7f7f >> (7 - shift
));
3220 tmp
|= png_ptr
->background
.gray
<< shift
;
3221 *sp
= (png_byte
)(tmp
& 0xff);
3238 #ifdef PNG_READ_GAMMA_SUPPORTED
3239 if (gamma_table
!= NULL
)
3243 for (i
= 0; i
< row_width
; i
++)
3245 if ((png_uint_16
)((*sp
>> shift
) & 0x03)
3246 == png_ptr
->trans_color
.gray
)
3248 unsigned int tmp
= *sp
& (0x3f3f >> (6 - shift
));
3249 tmp
|= png_ptr
->background
.gray
<< shift
;
3250 *sp
= (png_byte
)(tmp
& 0xff);
3255 unsigned int p
= (*sp
>> shift
) & 0x03;
3256 unsigned int g
= (gamma_table
[p
| (p
<< 2) |
3257 (p
<< 4) | (p
<< 6)] >> 6) & 0x03;
3258 unsigned int tmp
= *sp
& (0x3f3f >> (6 - shift
));
3260 *sp
= (png_byte
)(tmp
& 0xff);
3279 for (i
= 0; i
< row_width
; i
++)
3281 if ((png_uint_16
)((*sp
>> shift
) & 0x03)
3282 == png_ptr
->trans_color
.gray
)
3284 unsigned int tmp
= *sp
& (0x3f3f >> (6 - shift
));
3285 tmp
|= png_ptr
->background
.gray
<< shift
;
3286 *sp
= (png_byte
)(tmp
& 0xff);
3304 #ifdef PNG_READ_GAMMA_SUPPORTED
3305 if (gamma_table
!= NULL
)
3309 for (i
= 0; i
< row_width
; i
++)
3311 if ((png_uint_16
)((*sp
>> shift
) & 0x0f)
3312 == png_ptr
->trans_color
.gray
)
3314 unsigned int tmp
= *sp
& (0xf0f >> (4 - shift
));
3315 tmp
|= png_ptr
->background
.gray
<< shift
;
3316 *sp
= (png_byte
)(tmp
& 0xff);
3321 unsigned int p
= (*sp
>> shift
) & 0x0f;
3322 unsigned int g
= (gamma_table
[p
| (p
<< 4)] >> 4) &
3324 unsigned int tmp
= *sp
& (0xf0f >> (4 - shift
));
3326 *sp
= (png_byte
)(tmp
& 0xff);
3345 for (i
= 0; i
< row_width
; i
++)
3347 if ((png_uint_16
)((*sp
>> shift
) & 0x0f)
3348 == png_ptr
->trans_color
.gray
)
3350 unsigned int tmp
= *sp
& (0xf0f >> (4 - shift
));
3351 tmp
|= png_ptr
->background
.gray
<< shift
;
3352 *sp
= (png_byte
)(tmp
& 0xff);
3370 #ifdef PNG_READ_GAMMA_SUPPORTED
3371 if (gamma_table
!= NULL
)
3374 for (i
= 0; i
< row_width
; i
++, sp
++)
3376 if (*sp
== png_ptr
->trans_color
.gray
)
3377 *sp
= (png_byte
)png_ptr
->background
.gray
;
3380 *sp
= gamma_table
[*sp
];
3387 for (i
= 0; i
< row_width
; i
++, sp
++)
3389 if (*sp
== png_ptr
->trans_color
.gray
)
3390 *sp
= (png_byte
)png_ptr
->background
.gray
;
3398 #ifdef PNG_READ_GAMMA_SUPPORTED
3399 if (gamma_16
!= NULL
)
3402 for (i
= 0; i
< row_width
; i
++, sp
+= 2)
3406 v
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3408 if (v
== png_ptr
->trans_color
.gray
)
3410 /* Background is already in screen gamma */
3411 *sp
= (png_byte
)((png_ptr
->background
.gray
>> 8)
3413 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.gray
3419 v
= gamma_16
[*(sp
+ 1) >> gamma_shift
][*sp
];
3420 *sp
= (png_byte
)((v
>> 8) & 0xff);
3421 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3429 for (i
= 0; i
< row_width
; i
++, sp
+= 2)
3433 v
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3435 if (v
== png_ptr
->trans_color
.gray
)
3437 *sp
= (png_byte
)((png_ptr
->background
.gray
>> 8)
3439 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.gray
3453 case PNG_COLOR_TYPE_RGB
:
3455 if (row_info
->bit_depth
== 8)
3457 #ifdef PNG_READ_GAMMA_SUPPORTED
3458 if (gamma_table
!= NULL
)
3461 for (i
= 0; i
< row_width
; i
++, sp
+= 3)
3463 if (*sp
== png_ptr
->trans_color
.red
&&
3464 *(sp
+ 1) == png_ptr
->trans_color
.green
&&
3465 *(sp
+ 2) == png_ptr
->trans_color
.blue
)
3467 *sp
= (png_byte
)png_ptr
->background
.red
;
3468 *(sp
+ 1) = (png_byte
)png_ptr
->background
.green
;
3469 *(sp
+ 2) = (png_byte
)png_ptr
->background
.blue
;
3474 *sp
= gamma_table
[*sp
];
3475 *(sp
+ 1) = gamma_table
[*(sp
+ 1)];
3476 *(sp
+ 2) = gamma_table
[*(sp
+ 2)];
3484 for (i
= 0; i
< row_width
; i
++, sp
+= 3)
3486 if (*sp
== png_ptr
->trans_color
.red
&&
3487 *(sp
+ 1) == png_ptr
->trans_color
.green
&&
3488 *(sp
+ 2) == png_ptr
->trans_color
.blue
)
3490 *sp
= (png_byte
)png_ptr
->background
.red
;
3491 *(sp
+ 1) = (png_byte
)png_ptr
->background
.green
;
3492 *(sp
+ 2) = (png_byte
)png_ptr
->background
.blue
;
3497 else /* if (row_info->bit_depth == 16) */
3499 #ifdef PNG_READ_GAMMA_SUPPORTED
3500 if (gamma_16
!= NULL
)
3503 for (i
= 0; i
< row_width
; i
++, sp
+= 6)
3505 png_uint_16 r
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3507 png_uint_16 g
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3510 png_uint_16 b
= (png_uint_16
)(((*(sp
+ 4)) << 8)
3513 if (r
== png_ptr
->trans_color
.red
&&
3514 g
== png_ptr
->trans_color
.green
&&
3515 b
== png_ptr
->trans_color
.blue
)
3517 /* Background is already in screen gamma */
3518 *sp
= (png_byte
)((png_ptr
->background
.red
>> 8) & 0xff);
3519 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.red
& 0xff);
3520 *(sp
+ 2) = (png_byte
)((png_ptr
->background
.green
>> 8)
3522 *(sp
+ 3) = (png_byte
)(png_ptr
->background
.green
3524 *(sp
+ 4) = (png_byte
)((png_ptr
->background
.blue
>> 8)
3526 *(sp
+ 5) = (png_byte
)(png_ptr
->background
.blue
& 0xff);
3531 png_uint_16 v
= gamma_16
[*(sp
+ 1) >> gamma_shift
][*sp
];
3532 *sp
= (png_byte
)((v
>> 8) & 0xff);
3533 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3535 v
= gamma_16
[*(sp
+ 3) >> gamma_shift
][*(sp
+ 2)];
3536 *(sp
+ 2) = (png_byte
)((v
>> 8) & 0xff);
3537 *(sp
+ 3) = (png_byte
)(v
& 0xff);
3539 v
= gamma_16
[*(sp
+ 5) >> gamma_shift
][*(sp
+ 4)];
3540 *(sp
+ 4) = (png_byte
)((v
>> 8) & 0xff);
3541 *(sp
+ 5) = (png_byte
)(v
& 0xff);
3550 for (i
= 0; i
< row_width
; i
++, sp
+= 6)
3552 png_uint_16 r
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3554 png_uint_16 g
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3557 png_uint_16 b
= (png_uint_16
)(((*(sp
+ 4)) << 8)
3560 if (r
== png_ptr
->trans_color
.red
&&
3561 g
== png_ptr
->trans_color
.green
&&
3562 b
== png_ptr
->trans_color
.blue
)
3564 *sp
= (png_byte
)((png_ptr
->background
.red
>> 8) & 0xff);
3565 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.red
& 0xff);
3566 *(sp
+ 2) = (png_byte
)((png_ptr
->background
.green
>> 8)
3568 *(sp
+ 3) = (png_byte
)(png_ptr
->background
.green
3570 *(sp
+ 4) = (png_byte
)((png_ptr
->background
.blue
>> 8)
3572 *(sp
+ 5) = (png_byte
)(png_ptr
->background
.blue
& 0xff);
3580 case PNG_COLOR_TYPE_GRAY_ALPHA
:
3582 if (row_info
->bit_depth
== 8)
3584 #ifdef PNG_READ_GAMMA_SUPPORTED
3585 if (gamma_to_1
!= NULL
&& gamma_from_1
!= NULL
&&
3586 gamma_table
!= NULL
)
3589 for (i
= 0; i
< row_width
; i
++, sp
+= 2)
3591 png_uint_16 a
= *(sp
+ 1);
3594 *sp
= gamma_table
[*sp
];
3598 /* Background is already in screen gamma */
3599 *sp
= (png_byte
)png_ptr
->background
.gray
;
3606 v
= gamma_to_1
[*sp
];
3607 png_composite(w
, v
, a
, png_ptr
->background_1
.gray
);
3609 w
= gamma_from_1
[w
];
3618 for (i
= 0; i
< row_width
; i
++, sp
+= 2)
3620 png_byte a
= *(sp
+ 1);
3623 *sp
= (png_byte
)png_ptr
->background
.gray
;
3626 png_composite(*sp
, *sp
, a
, png_ptr
->background
.gray
);
3630 else /* if (png_ptr->bit_depth == 16) */
3632 #ifdef PNG_READ_GAMMA_SUPPORTED
3633 if (gamma_16
!= NULL
&& gamma_16_from_1
!= NULL
&&
3634 gamma_16_to_1
!= NULL
)
3637 for (i
= 0; i
< row_width
; i
++, sp
+= 4)
3639 png_uint_16 a
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3642 if (a
== (png_uint_16
)0xffff)
3646 v
= gamma_16
[*(sp
+ 1) >> gamma_shift
][*sp
];
3647 *sp
= (png_byte
)((v
>> 8) & 0xff);
3648 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3653 /* Background is already in screen gamma */
3654 *sp
= (png_byte
)((png_ptr
->background
.gray
>> 8)
3656 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.gray
& 0xff);
3661 png_uint_16 g
, v
, w
;
3663 g
= gamma_16_to_1
[*(sp
+ 1) >> gamma_shift
][*sp
];
3664 png_composite_16(v
, g
, a
, png_ptr
->background_1
.gray
);
3668 w
= gamma_16_from_1
[(v
&0xff) >> gamma_shift
][v
>> 8];
3669 *sp
= (png_byte
)((w
>> 8) & 0xff);
3670 *(sp
+ 1) = (png_byte
)(w
& 0xff);
3678 for (i
= 0; i
< row_width
; i
++, sp
+= 4)
3680 png_uint_16 a
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3685 *sp
= (png_byte
)((png_ptr
->background
.gray
>> 8)
3687 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.gray
& 0xff);
3690 else if (a
< 0xffff)
3694 g
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3695 png_composite_16(v
, g
, a
, png_ptr
->background
.gray
);
3696 *sp
= (png_byte
)((v
>> 8) & 0xff);
3697 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3705 case PNG_COLOR_TYPE_RGB_ALPHA
:
3707 if (row_info
->bit_depth
== 8)
3709 #ifdef PNG_READ_GAMMA_SUPPORTED
3710 if (gamma_to_1
!= NULL
&& gamma_from_1
!= NULL
&&
3711 gamma_table
!= NULL
)
3714 for (i
= 0; i
< row_width
; i
++, sp
+= 4)
3716 png_byte a
= *(sp
+ 3);
3720 *sp
= gamma_table
[*sp
];
3721 *(sp
+ 1) = gamma_table
[*(sp
+ 1)];
3722 *(sp
+ 2) = gamma_table
[*(sp
+ 2)];
3727 /* Background is already in screen gamma */
3728 *sp
= (png_byte
)png_ptr
->background
.red
;
3729 *(sp
+ 1) = (png_byte
)png_ptr
->background
.green
;
3730 *(sp
+ 2) = (png_byte
)png_ptr
->background
.blue
;
3737 v
= gamma_to_1
[*sp
];
3738 png_composite(w
, v
, a
, png_ptr
->background_1
.red
);
3739 if (!optimize
) w
= gamma_from_1
[w
];
3742 v
= gamma_to_1
[*(sp
+ 1)];
3743 png_composite(w
, v
, a
, png_ptr
->background_1
.green
);
3744 if (!optimize
) w
= gamma_from_1
[w
];
3747 v
= gamma_to_1
[*(sp
+ 2)];
3748 png_composite(w
, v
, a
, png_ptr
->background_1
.blue
);
3749 if (!optimize
) w
= gamma_from_1
[w
];
3758 for (i
= 0; i
< row_width
; i
++, sp
+= 4)
3760 png_byte a
= *(sp
+ 3);
3764 *sp
= (png_byte
)png_ptr
->background
.red
;
3765 *(sp
+ 1) = (png_byte
)png_ptr
->background
.green
;
3766 *(sp
+ 2) = (png_byte
)png_ptr
->background
.blue
;
3771 png_composite(*sp
, *sp
, a
, png_ptr
->background
.red
);
3773 png_composite(*(sp
+ 1), *(sp
+ 1), a
,
3774 png_ptr
->background
.green
);
3776 png_composite(*(sp
+ 2), *(sp
+ 2), a
,
3777 png_ptr
->background
.blue
);
3782 else /* if (row_info->bit_depth == 16) */
3784 #ifdef PNG_READ_GAMMA_SUPPORTED
3785 if (gamma_16
!= NULL
&& gamma_16_from_1
!= NULL
&&
3786 gamma_16_to_1
!= NULL
)
3789 for (i
= 0; i
< row_width
; i
++, sp
+= 8)
3791 png_uint_16 a
= (png_uint_16
)(((png_uint_16
)(*(sp
+ 6))
3792 << 8) + (png_uint_16
)(*(sp
+ 7)));
3794 if (a
== (png_uint_16
)0xffff)
3798 v
= gamma_16
[*(sp
+ 1) >> gamma_shift
][*sp
];
3799 *sp
= (png_byte
)((v
>> 8) & 0xff);
3800 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3802 v
= gamma_16
[*(sp
+ 3) >> gamma_shift
][*(sp
+ 2)];
3803 *(sp
+ 2) = (png_byte
)((v
>> 8) & 0xff);
3804 *(sp
+ 3) = (png_byte
)(v
& 0xff);
3806 v
= gamma_16
[*(sp
+ 5) >> gamma_shift
][*(sp
+ 4)];
3807 *(sp
+ 4) = (png_byte
)((v
>> 8) & 0xff);
3808 *(sp
+ 5) = (png_byte
)(v
& 0xff);
3813 /* Background is already in screen gamma */
3814 *sp
= (png_byte
)((png_ptr
->background
.red
>> 8) & 0xff);
3815 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.red
& 0xff);
3816 *(sp
+ 2) = (png_byte
)((png_ptr
->background
.green
>> 8)
3818 *(sp
+ 3) = (png_byte
)(png_ptr
->background
.green
3820 *(sp
+ 4) = (png_byte
)((png_ptr
->background
.blue
>> 8)
3822 *(sp
+ 5) = (png_byte
)(png_ptr
->background
.blue
& 0xff);
3829 v
= gamma_16_to_1
[*(sp
+ 1) >> gamma_shift
][*sp
];
3830 png_composite_16(w
, v
, a
, png_ptr
->background_1
.red
);
3832 w
= gamma_16_from_1
[((w
&0xff) >> gamma_shift
)][w
>>
3834 *sp
= (png_byte
)((w
>> 8) & 0xff);
3835 *(sp
+ 1) = (png_byte
)(w
& 0xff);
3837 v
= gamma_16_to_1
[*(sp
+ 3) >> gamma_shift
][*(sp
+ 2)];
3838 png_composite_16(w
, v
, a
, png_ptr
->background_1
.green
);
3840 w
= gamma_16_from_1
[((w
&0xff) >> gamma_shift
)][w
>>
3843 *(sp
+ 2) = (png_byte
)((w
>> 8) & 0xff);
3844 *(sp
+ 3) = (png_byte
)(w
& 0xff);
3846 v
= gamma_16_to_1
[*(sp
+ 5) >> gamma_shift
][*(sp
+ 4)];
3847 png_composite_16(w
, v
, a
, png_ptr
->background_1
.blue
);
3849 w
= gamma_16_from_1
[((w
&0xff) >> gamma_shift
)][w
>>
3852 *(sp
+ 4) = (png_byte
)((w
>> 8) & 0xff);
3853 *(sp
+ 5) = (png_byte
)(w
& 0xff);
3862 for (i
= 0; i
< row_width
; i
++, sp
+= 8)
3864 png_uint_16 a
= (png_uint_16
)(((png_uint_16
)(*(sp
+ 6))
3865 << 8) + (png_uint_16
)(*(sp
+ 7)));
3869 *sp
= (png_byte
)((png_ptr
->background
.red
>> 8) & 0xff);
3870 *(sp
+ 1) = (png_byte
)(png_ptr
->background
.red
& 0xff);
3871 *(sp
+ 2) = (png_byte
)((png_ptr
->background
.green
>> 8)
3873 *(sp
+ 3) = (png_byte
)(png_ptr
->background
.green
3875 *(sp
+ 4) = (png_byte
)((png_ptr
->background
.blue
>> 8)
3877 *(sp
+ 5) = (png_byte
)(png_ptr
->background
.blue
& 0xff);
3880 else if (a
< 0xffff)
3884 png_uint_16 r
= (png_uint_16
)(((*sp
) << 8) + *(sp
+ 1));
3885 png_uint_16 g
= (png_uint_16
)(((*(sp
+ 2)) << 8)
3887 png_uint_16 b
= (png_uint_16
)(((*(sp
+ 4)) << 8)
3890 png_composite_16(v
, r
, a
, png_ptr
->background
.red
);
3891 *sp
= (png_byte
)((v
>> 8) & 0xff);
3892 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3894 png_composite_16(v
, g
, a
, png_ptr
->background
.green
);
3895 *(sp
+ 2) = (png_byte
)((v
>> 8) & 0xff);
3896 *(sp
+ 3) = (png_byte
)(v
& 0xff);
3898 png_composite_16(v
, b
, a
, png_ptr
->background
.blue
);
3899 *(sp
+ 4) = (png_byte
)((v
>> 8) & 0xff);
3900 *(sp
+ 5) = (png_byte
)(v
& 0xff);
3913 #endif /* PNG_READ_BACKGROUND_SUPPORTED || PNG_READ_ALPHA_MODE_SUPPORTED */
3915 #ifdef PNG_READ_GAMMA_SUPPORTED
3916 /* Gamma correct the image, avoiding the alpha channel. Make sure
3917 * you do this after you deal with the transparency issue on grayscale
3918 * or RGB images. If your bit depth is 8, use gamma_table, if it
3919 * is 16, use gamma_16_table and gamma_shift. Build these with
3920 * build_gamma_table().
3923 png_do_gamma(png_row_infop row_info
, png_bytep row
, png_structrp png_ptr
)
3925 png_const_bytep gamma_table
= png_ptr
->gamma_table
;
3926 png_const_uint_16pp gamma_16_table
= png_ptr
->gamma_16_table
;
3927 int gamma_shift
= png_ptr
->gamma_shift
;
3931 png_uint_32 row_width
=row_info
->width
;
3933 png_debug(1, "in png_do_gamma");
3935 if (((row_info
->bit_depth
<= 8 && gamma_table
!= NULL
) ||
3936 (row_info
->bit_depth
== 16 && gamma_16_table
!= NULL
)))
3938 switch (row_info
->color_type
)
3940 case PNG_COLOR_TYPE_RGB
:
3942 if (row_info
->bit_depth
== 8)
3945 for (i
= 0; i
< row_width
; i
++)
3947 *sp
= gamma_table
[*sp
];
3949 *sp
= gamma_table
[*sp
];
3951 *sp
= gamma_table
[*sp
];
3956 else /* if (row_info->bit_depth == 16) */
3959 for (i
= 0; i
< row_width
; i
++)
3963 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
3964 *sp
= (png_byte
)((v
>> 8) & 0xff);
3965 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3968 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
3969 *sp
= (png_byte
)((v
>> 8) & 0xff);
3970 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3973 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
3974 *sp
= (png_byte
)((v
>> 8) & 0xff);
3975 *(sp
+ 1) = (png_byte
)(v
& 0xff);
3982 case PNG_COLOR_TYPE_RGB_ALPHA
:
3984 if (row_info
->bit_depth
== 8)
3987 for (i
= 0; i
< row_width
; i
++)
3989 *sp
= gamma_table
[*sp
];
3992 *sp
= gamma_table
[*sp
];
3995 *sp
= gamma_table
[*sp
];
4002 else /* if (row_info->bit_depth == 16) */
4005 for (i
= 0; i
< row_width
; i
++)
4007 png_uint_16 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4008 *sp
= (png_byte
)((v
>> 8) & 0xff);
4009 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4012 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4013 *sp
= (png_byte
)((v
>> 8) & 0xff);
4014 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4017 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4018 *sp
= (png_byte
)((v
>> 8) & 0xff);
4019 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4026 case PNG_COLOR_TYPE_GRAY_ALPHA
:
4028 if (row_info
->bit_depth
== 8)
4031 for (i
= 0; i
< row_width
; i
++)
4033 *sp
= gamma_table
[*sp
];
4038 else /* if (row_info->bit_depth == 16) */
4041 for (i
= 0; i
< row_width
; i
++)
4043 png_uint_16 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4044 *sp
= (png_byte
)((v
>> 8) & 0xff);
4045 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4052 case PNG_COLOR_TYPE_GRAY
:
4054 if (row_info
->bit_depth
== 2)
4057 for (i
= 0; i
< row_width
; i
+= 4)
4065 ((((int)gamma_table
[a
|(a
>>2)|(a
>>4)|(a
>>6)]) ) & 0xc0)|
4066 ((((int)gamma_table
[(b
<<2)|b
|(b
>>2)|(b
>>4)])>>2) & 0x30)|
4067 ((((int)gamma_table
[(c
<<4)|(c
<<2)|c
|(c
>>2)])>>4) & 0x0c)|
4068 ((((int)gamma_table
[(d
<<6)|(d
<<4)|(d
<<2)|d
])>>6) ));
4073 if (row_info
->bit_depth
== 4)
4076 for (i
= 0; i
< row_width
; i
+= 2)
4078 int msb
= *sp
& 0xf0;
4079 int lsb
= *sp
& 0x0f;
4081 *sp
= (png_byte
)((((int)gamma_table
[msb
| (msb
>> 4)]) & 0xf0)
4082 | (((int)gamma_table
[(lsb
<< 4) | lsb
]) >> 4));
4087 else if (row_info
->bit_depth
== 8)
4090 for (i
= 0; i
< row_width
; i
++)
4092 *sp
= gamma_table
[*sp
];
4097 else if (row_info
->bit_depth
== 16)
4100 for (i
= 0; i
< row_width
; i
++)
4102 png_uint_16 v
= gamma_16_table
[*(sp
+ 1) >> gamma_shift
][*sp
];
4103 *sp
= (png_byte
)((v
>> 8) & 0xff);
4104 *(sp
+ 1) = (png_byte
)(v
& 0xff);
4118 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
4119 /* Encode the alpha channel to the output gamma (the input channel is always
4120 * linear.) Called only with color types that have an alpha channel. Needs the
4124 png_do_encode_alpha(png_row_infop row_info
, png_bytep row
, png_structrp png_ptr
)
4126 png_uint_32 row_width
= row_info
->width
;
4128 png_debug(1, "in png_do_encode_alpha");
4130 if (row_info
->color_type
& PNG_COLOR_MASK_ALPHA
)
4132 if (row_info
->bit_depth
== 8)
4134 PNG_CONST png_bytep table
= png_ptr
->gamma_from_1
;
4138 PNG_CONST
int step
=
4139 (row_info
->color_type
& PNG_COLOR_MASK_COLOR
) ?
4 : 2;
4141 /* The alpha channel is the last component: */
4144 for (; row_width
> 0; --row_width
, row
+= step
)
4151 else if (row_info
->bit_depth
== 16)
4153 PNG_CONST png_uint_16pp table
= png_ptr
->gamma_16_from_1
;
4154 PNG_CONST
int gamma_shift
= png_ptr
->gamma_shift
;
4158 PNG_CONST
int step
=
4159 (row_info
->color_type
& PNG_COLOR_MASK_COLOR
) ?
8 : 4;
4161 /* The alpha channel is the last component: */
4164 for (; row_width
> 0; --row_width
, row
+= step
)
4168 v
= table
[*(row
+ 1) >> gamma_shift
][*row
];
4169 *row
= (png_byte
)((v
>> 8) & 0xff);
4170 *(row
+ 1) = (png_byte
)(v
& 0xff);
4178 /* Only get to here if called with a weird row_info; no harm has been done,
4179 * so just issue a warning.
4181 png_warning(png_ptr
, "png_do_encode_alpha: unexpected call");
4185 #ifdef PNG_READ_EXPAND_SUPPORTED
4186 /* Expands a palette row to an RGB or RGBA row depending
4187 * upon whether you supply trans and num_trans.
4190 png_do_expand_palette(png_row_infop row_info
, png_bytep row
,
4191 png_const_colorp palette
, png_const_bytep trans_alpha
, int num_trans
)
4196 png_uint_32 row_width
=row_info
->width
;
4198 png_debug(1, "in png_do_expand_palette");
4200 if (row_info
->color_type
== PNG_COLOR_TYPE_PALETTE
)
4202 if (row_info
->bit_depth
< 8)
4204 switch (row_info
->bit_depth
)
4208 sp
= row
+ (png_size_t
)((row_width
- 1) >> 3);
4209 dp
= row
+ (png_size_t
)row_width
- 1;
4210 shift
= 7 - (int)((row_width
+ 7) & 0x07);
4211 for (i
= 0; i
< row_width
; i
++)
4213 if ((*sp
>> shift
) & 0x01)
4235 sp
= row
+ (png_size_t
)((row_width
- 1) >> 2);
4236 dp
= row
+ (png_size_t
)row_width
- 1;
4237 shift
= (int)((3 - ((row_width
+ 3) & 0x03)) << 1);
4238 for (i
= 0; i
< row_width
; i
++)
4240 value
= (*sp
>> shift
) & 0x03;
4241 *dp
= (png_byte
)value
;
4258 sp
= row
+ (png_size_t
)((row_width
- 1) >> 1);
4259 dp
= row
+ (png_size_t
)row_width
- 1;
4260 shift
= (int)((row_width
& 0x01) << 2);
4261 for (i
= 0; i
< row_width
; i
++)
4263 value
= (*sp
>> shift
) & 0x0f;
4264 *dp
= (png_byte
)value
;
4282 row_info
->bit_depth
= 8;
4283 row_info
->pixel_depth
= 8;
4284 row_info
->rowbytes
= row_width
;
4287 if (row_info
->bit_depth
== 8)
4292 sp
= row
+ (png_size_t
)row_width
- 1;
4293 dp
= row
+ (png_size_t
)(row_width
<< 2) - 1;
4295 for (i
= 0; i
< row_width
; i
++)
4297 if ((int)(*sp
) >= num_trans
)
4301 *dp
-- = trans_alpha
[*sp
];
4303 *dp
-- = palette
[*sp
].blue
;
4304 *dp
-- = palette
[*sp
].green
;
4305 *dp
-- = palette
[*sp
].red
;
4308 row_info
->bit_depth
= 8;
4309 row_info
->pixel_depth
= 32;
4310 row_info
->rowbytes
= row_width
* 4;
4311 row_info
->color_type
= 6;
4312 row_info
->channels
= 4;
4317 sp
= row
+ (png_size_t
)row_width
- 1;
4318 dp
= row
+ (png_size_t
)(row_width
* 3) - 1;
4320 for (i
= 0; i
< row_width
; i
++)
4322 *dp
-- = palette
[*sp
].blue
;
4323 *dp
-- = palette
[*sp
].green
;
4324 *dp
-- = palette
[*sp
].red
;
4328 row_info
->bit_depth
= 8;
4329 row_info
->pixel_depth
= 24;
4330 row_info
->rowbytes
= row_width
* 3;
4331 row_info
->color_type
= 2;
4332 row_info
->channels
= 3;
4339 /* If the bit depth < 8, it is expanded to 8. Also, if the already
4340 * expanded transparency value is supplied, an alpha channel is built.
4343 png_do_expand(png_row_infop row_info
, png_bytep row
,
4344 png_const_color_16p trans_color
)
4349 png_uint_32 row_width
=row_info
->width
;
4351 png_debug(1, "in png_do_expand");
4354 if (row_info
->color_type
== PNG_COLOR_TYPE_GRAY
)
4356 unsigned int gray
= trans_color ? trans_color
->gray
: 0;
4358 if (row_info
->bit_depth
< 8)
4360 switch (row_info
->bit_depth
)
4364 gray
= (gray
& 0x01) * 0xff;
4365 sp
= row
+ (png_size_t
)((row_width
- 1) >> 3);
4366 dp
= row
+ (png_size_t
)row_width
- 1;
4367 shift
= 7 - (int)((row_width
+ 7) & 0x07);
4368 for (i
= 0; i
< row_width
; i
++)
4370 if ((*sp
>> shift
) & 0x01)
4392 gray
= (gray
& 0x03) * 0x55;
4393 sp
= row
+ (png_size_t
)((row_width
- 1) >> 2);
4394 dp
= row
+ (png_size_t
)row_width
- 1;
4395 shift
= (int)((3 - ((row_width
+ 3) & 0x03)) << 1);
4396 for (i
= 0; i
< row_width
; i
++)
4398 value
= (*sp
>> shift
) & 0x03;
4399 *dp
= (png_byte
)(value
| (value
<< 2) | (value
<< 4) |
4417 gray
= (gray
& 0x0f) * 0x11;
4418 sp
= row
+ (png_size_t
)((row_width
- 1) >> 1);
4419 dp
= row
+ (png_size_t
)row_width
- 1;
4420 shift
= (int)((1 - ((row_width
+ 1) & 0x01)) << 2);
4421 for (i
= 0; i
< row_width
; i
++)
4423 value
= (*sp
>> shift
) & 0x0f;
4424 *dp
= (png_byte
)(value
| (value
<< 4));
4443 row_info
->bit_depth
= 8;
4444 row_info
->pixel_depth
= 8;
4445 row_info
->rowbytes
= row_width
;
4448 if (trans_color
!= NULL
)
4450 if (row_info
->bit_depth
== 8)
4453 sp
= row
+ (png_size_t
)row_width
- 1;
4454 dp
= row
+ (png_size_t
)(row_width
<< 1) - 1;
4456 for (i
= 0; i
< row_width
; i
++)
4468 else if (row_info
->bit_depth
== 16)
4470 unsigned int gray_high
= (gray
>> 8) & 0xff;
4471 unsigned int gray_low
= gray
& 0xff;
4472 sp
= row
+ row_info
->rowbytes
- 1;
4473 dp
= row
+ (row_info
->rowbytes
<< 1) - 1;
4474 for (i
= 0; i
< row_width
; i
++)
4476 if (*(sp
- 1) == gray_high
&& *(sp
) == gray_low
)
4493 row_info
->color_type
= PNG_COLOR_TYPE_GRAY_ALPHA
;
4494 row_info
->channels
= 2;
4495 row_info
->pixel_depth
= (png_byte
)(row_info
->bit_depth
<< 1);
4496 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
,
4500 else if (row_info
->color_type
== PNG_COLOR_TYPE_RGB
&& trans_color
)
4502 if (row_info
->bit_depth
== 8)
4504 png_byte red
= (png_byte
)(trans_color
->red
& 0xff);
4505 png_byte green
= (png_byte
)(trans_color
->green
& 0xff);
4506 png_byte blue
= (png_byte
)(trans_color
->blue
& 0xff);
4507 sp
= row
+ (png_size_t
)row_info
->rowbytes
- 1;
4508 dp
= row
+ (png_size_t
)(row_width
<< 2) - 1;
4509 for (i
= 0; i
< row_width
; i
++)
4511 if (*(sp
- 2) == red
&& *(sp
- 1) == green
&& *(sp
) == blue
)
4522 else if (row_info
->bit_depth
== 16)
4524 png_byte red_high
= (png_byte
)((trans_color
->red
>> 8) & 0xff);
4525 png_byte green_high
= (png_byte
)((trans_color
->green
>> 8) & 0xff);
4526 png_byte blue_high
= (png_byte
)((trans_color
->blue
>> 8) & 0xff);
4527 png_byte red_low
= (png_byte
)(trans_color
->red
& 0xff);
4528 png_byte green_low
= (png_byte
)(trans_color
->green
& 0xff);
4529 png_byte blue_low
= (png_byte
)(trans_color
->blue
& 0xff);
4530 sp
= row
+ row_info
->rowbytes
- 1;
4531 dp
= row
+ (png_size_t
)(row_width
<< 3) - 1;
4532 for (i
= 0; i
< row_width
; i
++)
4534 if (*(sp
- 5) == red_high
&&
4535 *(sp
- 4) == red_low
&&
4536 *(sp
- 3) == green_high
&&
4537 *(sp
- 2) == green_low
&&
4538 *(sp
- 1) == blue_high
&&
4559 row_info
->color_type
= PNG_COLOR_TYPE_RGB_ALPHA
;
4560 row_info
->channels
= 4;
4561 row_info
->pixel_depth
= (png_byte
)(row_info
->bit_depth
<< 2);
4562 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
4568 #ifdef PNG_READ_EXPAND_16_SUPPORTED
4569 /* If the bit depth is 8 and the color type is not a palette type expand the
4570 * whole row to 16 bits. Has no effect otherwise.
4573 png_do_expand_16(png_row_infop row_info
, png_bytep row
)
4575 if (row_info
->bit_depth
== 8 &&
4576 row_info
->color_type
!= PNG_COLOR_TYPE_PALETTE
)
4578 /* The row have a sequence of bytes containing [0..255] and we need
4579 * to turn it into another row containing [0..65535], to do this we
4582 * (input / 255) * 65535
4584 * Which happens to be exactly input * 257 and this can be achieved
4585 * simply by byte replication in place (copying backwards).
4587 png_byte
*sp
= row
+ row_info
->rowbytes
; /* source, last byte + 1 */
4588 png_byte
*dp
= sp
+ row_info
->rowbytes
; /* destination, end + 1 */
4590 dp
[-2] = dp
[-1] = *--sp
, dp
-= 2;
4592 row_info
->rowbytes
*= 2;
4593 row_info
->bit_depth
= 16;
4594 row_info
->pixel_depth
= (png_byte
)(row_info
->channels
* 16);
4599 #ifdef PNG_READ_QUANTIZE_SUPPORTED
4601 png_do_quantize(png_row_infop row_info
, png_bytep row
,
4602 png_const_bytep palette_lookup
, png_const_bytep quantize_lookup
)
4606 png_uint_32 row_width
=row_info
->width
;
4608 png_debug(1, "in png_do_quantize");
4610 if (row_info
->bit_depth
== 8)
4612 if (row_info
->color_type
== PNG_COLOR_TYPE_RGB
&& palette_lookup
)
4617 for (i
= 0; i
< row_width
; i
++)
4623 /* This looks real messy, but the compiler will reduce
4624 * it down to a reasonable formula. For example, with
4625 * 5 bits per color, we get:
4626 * p = (((r >> 3) & 0x1f) << 10) |
4627 * (((g >> 3) & 0x1f) << 5) |
4628 * ((b >> 3) & 0x1f);
4630 p
= (((r
>> (8 - PNG_QUANTIZE_RED_BITS
)) &
4631 ((1 << PNG_QUANTIZE_RED_BITS
) - 1)) <<
4632 (PNG_QUANTIZE_GREEN_BITS
+ PNG_QUANTIZE_BLUE_BITS
)) |
4633 (((g
>> (8 - PNG_QUANTIZE_GREEN_BITS
)) &
4634 ((1 << PNG_QUANTIZE_GREEN_BITS
) - 1)) <<
4635 (PNG_QUANTIZE_BLUE_BITS
)) |
4636 ((b
>> (8 - PNG_QUANTIZE_BLUE_BITS
)) &
4637 ((1 << PNG_QUANTIZE_BLUE_BITS
) - 1));
4639 *dp
++ = palette_lookup
[p
];
4642 row_info
->color_type
= PNG_COLOR_TYPE_PALETTE
;
4643 row_info
->channels
= 1;
4644 row_info
->pixel_depth
= row_info
->bit_depth
;
4645 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
4648 else if (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
&&
4649 palette_lookup
!= NULL
)
4654 for (i
= 0; i
< row_width
; i
++)
4661 p
= (((r
>> (8 - PNG_QUANTIZE_RED_BITS
)) &
4662 ((1 << PNG_QUANTIZE_RED_BITS
) - 1)) <<
4663 (PNG_QUANTIZE_GREEN_BITS
+ PNG_QUANTIZE_BLUE_BITS
)) |
4664 (((g
>> (8 - PNG_QUANTIZE_GREEN_BITS
)) &
4665 ((1 << PNG_QUANTIZE_GREEN_BITS
) - 1)) <<
4666 (PNG_QUANTIZE_BLUE_BITS
)) |
4667 ((b
>> (8 - PNG_QUANTIZE_BLUE_BITS
)) &
4668 ((1 << PNG_QUANTIZE_BLUE_BITS
) - 1));
4670 *dp
++ = palette_lookup
[p
];
4673 row_info
->color_type
= PNG_COLOR_TYPE_PALETTE
;
4674 row_info
->channels
= 1;
4675 row_info
->pixel_depth
= row_info
->bit_depth
;
4676 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_width
);
4679 else if (row_info
->color_type
== PNG_COLOR_TYPE_PALETTE
&&
4684 for (i
= 0; i
< row_width
; i
++, sp
++)
4686 *sp
= quantize_lookup
[*sp
];
4691 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
4693 /* Transform the row. The order of transformations is significant,
4694 * and is very touchy. If you add a transformation, take care to
4695 * decide how it fits in with the other transformations here.
4698 png_do_read_transformations(png_structrp png_ptr
, png_row_infop row_info
)
4700 png_debug(1, "in png_do_read_transformations");
4702 if (png_ptr
->row_buf
== NULL
)
4704 /* Prior to 1.5.4 this output row/pass where the NULL pointer is, but this
4705 * error is incredibly rare and incredibly easy to debug without this
4708 png_error(png_ptr
, "NULL row buffer");
4711 /* The following is debugging; prior to 1.5.4 the code was never compiled in;
4712 * in 1.5.4 PNG_FLAG_DETECT_UNINITIALIZED was added and the macro
4713 * PNG_WARN_UNINITIALIZED_ROW removed. In 1.6 the new flag is set only for
4714 * all transformations, however in practice the ROW_INIT always gets done on
4715 * demand, if necessary.
4717 if ((png_ptr
->flags
& PNG_FLAG_DETECT_UNINITIALIZED
) != 0 &&
4718 !(png_ptr
->flags
& PNG_FLAG_ROW_INIT
))
4720 /* Application has failed to call either png_read_start_image() or
4721 * png_read_update_info() after setting transforms that expand pixels.
4722 * This check added to libpng-1.2.19 (but not enabled until 1.5.4).
4724 png_error(png_ptr
, "Uninitialized row");
4727 #ifdef PNG_READ_EXPAND_SUPPORTED
4728 if (png_ptr
->transformations
& PNG_EXPAND
)
4730 if (row_info
->color_type
== PNG_COLOR_TYPE_PALETTE
)
4732 png_do_expand_palette(row_info
, png_ptr
->row_buf
+ 1,
4733 png_ptr
->palette
, png_ptr
->trans_alpha
, png_ptr
->num_trans
);
4738 if (png_ptr
->num_trans
&&
4739 (png_ptr
->transformations
& PNG_EXPAND_tRNS
))
4740 png_do_expand(row_info
, png_ptr
->row_buf
+ 1,
4741 &(png_ptr
->trans_color
));
4744 png_do_expand(row_info
, png_ptr
->row_buf
+ 1,
4750 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
4751 if ((png_ptr
->transformations
& PNG_STRIP_ALPHA
) &&
4752 !(png_ptr
->transformations
& PNG_COMPOSE
) &&
4753 (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
||
4754 row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
))
4755 png_do_strip_channel(row_info
, png_ptr
->row_buf
+ 1,
4756 0 /* at_start == false, because SWAP_ALPHA happens later */);
4759 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
4760 if (png_ptr
->transformations
& PNG_RGB_TO_GRAY
)
4763 png_do_rgb_to_gray(png_ptr
, row_info
,
4764 png_ptr
->row_buf
+ 1);
4768 png_ptr
->rgb_to_gray_status
=1;
4769 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) ==
4770 PNG_RGB_TO_GRAY_WARN
)
4771 png_warning(png_ptr
, "png_do_rgb_to_gray found nongray pixel");
4773 if ((png_ptr
->transformations
& PNG_RGB_TO_GRAY
) ==
4774 PNG_RGB_TO_GRAY_ERR
)
4775 png_error(png_ptr
, "png_do_rgb_to_gray found nongray pixel");
4780 /* From Andreas Dilger e-mail to png-implement, 26 March 1998:
4782 * In most cases, the "simple transparency" should be done prior to doing
4783 * gray-to-RGB, or you will have to test 3x as many bytes to check if a
4784 * pixel is transparent. You would also need to make sure that the
4785 * transparency information is upgraded to RGB.
4787 * To summarize, the current flow is:
4788 * - Gray + simple transparency -> compare 1 or 2 gray bytes and composite
4789 * with background "in place" if transparent,
4790 * convert to RGB if necessary
4791 * - Gray + alpha -> composite with gray background and remove alpha bytes,
4792 * convert to RGB if necessary
4794 * To support RGB backgrounds for gray images we need:
4795 * - Gray + simple transparency -> convert to RGB + simple transparency,
4796 * compare 3 or 6 bytes and composite with
4797 * background "in place" if transparent
4798 * (3x compare/pixel compared to doing
4799 * composite with gray bkgrnd)
4800 * - Gray + alpha -> convert to RGB + alpha, composite with background and
4801 * remove alpha bytes (3x float
4802 * operations/pixel compared with composite
4803 * on gray background)
4805 * Greg's change will do this. The reason it wasn't done before is for
4806 * performance, as this increases the per-pixel operations. If we would check
4807 * in advance if the background was gray or RGB, and position the gray-to-RGB
4808 * transform appropriately, then it would save a lot of work/time.
4811 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
4812 /* If gray -> RGB, do so now only if background is non-gray; else do later
4813 * for performance reasons
4815 if ((png_ptr
->transformations
& PNG_GRAY_TO_RGB
) &&
4816 !(png_ptr
->mode
& PNG_BACKGROUND_IS_GRAY
))
4817 png_do_gray_to_rgb(row_info
, png_ptr
->row_buf
+ 1);
4820 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
4821 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
4822 if (png_ptr
->transformations
& PNG_COMPOSE
)
4823 png_do_compose(row_info
, png_ptr
->row_buf
+ 1, png_ptr
);
4826 #ifdef PNG_READ_GAMMA_SUPPORTED
4827 if ((png_ptr
->transformations
& PNG_GAMMA
) &&
4828 #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
4829 /* Because RGB_TO_GRAY does the gamma transform. */
4830 !(png_ptr
->transformations
& PNG_RGB_TO_GRAY
) &&
4832 #if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
4833 defined(PNG_READ_ALPHA_MODE_SUPPORTED)
4834 /* Because PNG_COMPOSE does the gamma transform if there is something to
4835 * do (if there is an alpha channel or transparency.)
4837 !((png_ptr
->transformations
& PNG_COMPOSE
) &&
4838 ((png_ptr
->num_trans
!= 0) ||
4839 (png_ptr
->color_type
& PNG_COLOR_MASK_ALPHA
))) &&
4841 /* Because png_init_read_transformations transforms the palette, unless
4842 * RGB_TO_GRAY will do the transform.
4844 (png_ptr
->color_type
!= PNG_COLOR_TYPE_PALETTE
))
4845 png_do_gamma(row_info
, png_ptr
->row_buf
+ 1, png_ptr
);
4848 #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
4849 if ((png_ptr
->transformations
& PNG_STRIP_ALPHA
) &&
4850 (png_ptr
->transformations
& PNG_COMPOSE
) &&
4851 (row_info
->color_type
== PNG_COLOR_TYPE_RGB_ALPHA
||
4852 row_info
->color_type
== PNG_COLOR_TYPE_GRAY_ALPHA
))
4853 png_do_strip_channel(row_info
, png_ptr
->row_buf
+ 1,
4854 0 /* at_start == false, because SWAP_ALPHA happens later */);
4857 #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
4858 if ((png_ptr
->transformations
& PNG_ENCODE_ALPHA
) &&
4859 (row_info
->color_type
& PNG_COLOR_MASK_ALPHA
))
4860 png_do_encode_alpha(row_info
, png_ptr
->row_buf
+ 1, png_ptr
);
4863 #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
4864 if (png_ptr
->transformations
& PNG_SCALE_16_TO_8
)
4865 png_do_scale_16_to_8(row_info
, png_ptr
->row_buf
+ 1);
4868 #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
4869 /* There is no harm in doing both of these because only one has any effect,
4870 * by putting the 'scale' option first if the app asks for scale (either by
4871 * calling the API or in a TRANSFORM flag) this is what happens.
4873 if (png_ptr
->transformations
& PNG_16_TO_8
)
4874 png_do_chop(row_info
, png_ptr
->row_buf
+ 1);
4877 #ifdef PNG_READ_QUANTIZE_SUPPORTED
4878 if (png_ptr
->transformations
& PNG_QUANTIZE
)
4880 png_do_quantize(row_info
, png_ptr
->row_buf
+ 1,
4881 png_ptr
->palette_lookup
, png_ptr
->quantize_index
);
4883 if (row_info
->rowbytes
== 0)
4884 png_error(png_ptr
, "png_do_quantize returned rowbytes=0");
4886 #endif /* PNG_READ_QUANTIZE_SUPPORTED */
4888 #ifdef PNG_READ_EXPAND_16_SUPPORTED
4889 /* Do the expansion now, after all the arithmetic has been done. Notice
4890 * that previous transformations can handle the PNG_EXPAND_16 flag if this
4891 * is efficient (particularly true in the case of gamma correction, where
4892 * better accuracy results faster!)
4894 if (png_ptr
->transformations
& PNG_EXPAND_16
)
4895 png_do_expand_16(row_info
, png_ptr
->row_buf
+ 1);
4898 #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
4899 /* NOTE: moved here in 1.5.4 (from much later in this list.) */
4900 if ((png_ptr
->transformations
& PNG_GRAY_TO_RGB
) &&
4901 (png_ptr
->mode
& PNG_BACKGROUND_IS_GRAY
))
4902 png_do_gray_to_rgb(row_info
, png_ptr
->row_buf
+ 1);
4905 #ifdef PNG_READ_INVERT_SUPPORTED
4906 if (png_ptr
->transformations
& PNG_INVERT_MONO
)
4907 png_do_invert(row_info
, png_ptr
->row_buf
+ 1);
4910 #ifdef PNG_READ_SHIFT_SUPPORTED
4911 if (png_ptr
->transformations
& PNG_SHIFT
)
4912 png_do_unshift(row_info
, png_ptr
->row_buf
+ 1,
4916 #ifdef PNG_READ_PACK_SUPPORTED
4917 if (png_ptr
->transformations
& PNG_PACK
)
4918 png_do_unpack(row_info
, png_ptr
->row_buf
+ 1);
4921 #ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
4922 /* Added at libpng-1.5.10 */
4923 if (row_info
->color_type
== PNG_COLOR_TYPE_PALETTE
&&
4924 png_ptr
->num_palette_max
>= 0)
4925 png_do_check_palette_indexes(png_ptr
, row_info
);
4928 #ifdef PNG_READ_BGR_SUPPORTED
4929 if (png_ptr
->transformations
& PNG_BGR
)
4930 png_do_bgr(row_info
, png_ptr
->row_buf
+ 1);
4933 #ifdef PNG_READ_PACKSWAP_SUPPORTED
4934 if (png_ptr
->transformations
& PNG_PACKSWAP
)
4935 png_do_packswap(row_info
, png_ptr
->row_buf
+ 1);
4938 #ifdef PNG_READ_FILLER_SUPPORTED
4939 if (png_ptr
->transformations
& PNG_FILLER
)
4940 png_do_read_filler(row_info
, png_ptr
->row_buf
+ 1,
4941 (png_uint_32
)png_ptr
->filler
, png_ptr
->flags
);
4944 #ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
4945 if (png_ptr
->transformations
& PNG_INVERT_ALPHA
)
4946 png_do_read_invert_alpha(row_info
, png_ptr
->row_buf
+ 1);
4949 #ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
4950 if (png_ptr
->transformations
& PNG_SWAP_ALPHA
)
4951 png_do_read_swap_alpha(row_info
, png_ptr
->row_buf
+ 1);
4954 #ifdef PNG_READ_16BIT_SUPPORTED
4955 #ifdef PNG_READ_SWAP_SUPPORTED
4956 if (png_ptr
->transformations
& PNG_SWAP_BYTES
)
4957 png_do_swap(row_info
, png_ptr
->row_buf
+ 1);
4961 #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
4962 if (png_ptr
->transformations
& PNG_USER_TRANSFORM
)
4964 if (png_ptr
->read_user_transform_fn
!= NULL
)
4965 (*(png_ptr
->read_user_transform_fn
)) /* User read transform function */
4966 (png_ptr
, /* png_ptr */
4967 row_info
, /* row_info: */
4968 /* png_uint_32 width; width of row */
4969 /* png_size_t rowbytes; number of bytes in row */
4970 /* png_byte color_type; color type of pixels */
4971 /* png_byte bit_depth; bit depth of samples */
4972 /* png_byte channels; number of channels (1-4) */
4973 /* png_byte pixel_depth; bits per pixel (depth*channels) */
4974 png_ptr
->row_buf
+ 1); /* start of pixel data for row */
4975 #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
4976 if (png_ptr
->user_transform_depth
)
4977 row_info
->bit_depth
= png_ptr
->user_transform_depth
;
4979 if (png_ptr
->user_transform_channels
)
4980 row_info
->channels
= png_ptr
->user_transform_channels
;
4982 row_info
->pixel_depth
= (png_byte
)(row_info
->bit_depth
*
4983 row_info
->channels
);
4985 row_info
->rowbytes
= PNG_ROWBYTES(row_info
->pixel_depth
, row_info
->width
);
4990 #endif /* PNG_READ_TRANSFORMS_SUPPORTED */
4991 #endif /* PNG_READ_SUPPORTED */