share/png/contrib/gregbook/readpng.c

   1 /*---------------------------------------------------------------------------
   2
   3    rpng - simple PNG display program                              readpng.c
   4
   5   ---------------------------------------------------------------------------
   6
   7       Copyright (c) 1998-2007 Greg Roelofs.  All rights reserved.
   8
   9       This software is provided "as is," without warranty of any kind,
  10       express or implied.  In no event shall the author or contributors
  11       be held liable for any damages arising in any way from the use of
  12       this software.
  13
  14       The contents of this file are DUAL-LICENSED.  You may modify and/or
  15       redistribute this software according to the terms of one of the
  16       following two licenses (at your option):
  17
  18
  19       LICENSE 1 ("BSD-like with advertising clause"):
  20
  21       Permission is granted to anyone to use this software for any purpose,
  22       including commercial applications, and to alter it and redistribute
  23       it freely, subject to the following restrictions:
  24
  25       1. Redistributions of source code must retain the above copyright
  26          notice, disclaimer, and this list of conditions.
  27       2. Redistributions in binary form must reproduce the above copyright
  28          notice, disclaimer, and this list of conditions in the documenta-
  29          tion and/or other materials provided with the distribution.
  30       3. All advertising materials mentioning features or use of this
  31          software must display the following acknowledgment:
  32
  33             This product includes software developed by Greg Roelofs
  34             and contributors for the book, "PNG: The Definitive Guide,"
  35             published by O'Reilly and Associates.
  36
  37
  38       LICENSE 2 (GNU GPL v2 or later):
  39
  40       This program is free software; you can redistribute it and/or modify
  41       it under the terms of the GNU General Public License as published by
  42       the Free Software Foundation; either version 2 of the License, or
  43       (at your option) any later version.
  44
  45       This program is distributed in the hope that it will be useful,
  46       but WITHOUT ANY WARRANTY; without even the implied warranty of
  47       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  48       GNU General Public License for more details.
  49
  50       You should have received a copy of the GNU General Public License
  51       along with this program; if not, write to the Free Software Foundation,
  52       Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  53
  54   ---------------------------------------------------------------------------*/
  55
  56 #include <stdio.h>
  57 #include <stdlib.h>
  58 #include <zlib.h>
  59
  60 #include "png.h"        /* libpng header */
  61 #include "readpng.h"    /* typedefs, common macros, public prototypes */
  62
  63 /* future versions of libpng will provide this macro: */
  64 #ifndef png_jmpbuf
  65 #  define png_jmpbuf(png_ptr)   ((png_ptr)->jmpbuf)
  66 #endif
  67
  68
  69 static png_structp png_ptr = NULL;
  70 static png_infop info_ptr = NULL;
  71
  72 png_uint_32  width, height;
  73 int  bit_depth, color_type;
  74 uch  *image_data = NULL;
  75
  76
  77 void readpng_version_info(void)
  78 {
  79     fprintf(stderr, "   Compiled with libpng %s; using libpng %s.\n",
  80       PNG_LIBPNG_VER_STRING, png_libpng_ver);
  81     fprintf(stderr, "   Compiled with zlib %s; using zlib %s.\n",
  82       ZLIB_VERSION, zlib_version);
  83 }
  84
  85
  86 /* return value = 0 for success, 1 for bad sig, 2 for bad IHDR, 4 for no mem */
  87
  88 int readpng_init(FILE *infile, ulg *pWidth, ulg *pHeight)
  89 {
  90     uch sig[8];
  91
  92
  93     /* first do a quick check that the file really is a PNG image; could
  94      * have used slightly more general png_sig_cmp() function instead */
  95
  96     fread(sig, 1, 8, infile);
  97     if (png_sig_cmp(sig, 0, 8))
  98         return 1;   /* bad signature */
  99
 100
 101     /* could pass pointers to user-defined error handlers instead of NULLs: */
 102
 103     png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
 104     if (!png_ptr)
 105         return 4;   /* out of memory */
 106
 107     info_ptr = png_create_info_struct(png_ptr);
 108     if (!info_ptr) {
 109         png_destroy_read_struct(&png_ptr, NULL, NULL);
 110         return 4;   /* out of memory */
 111     }
 112
 113
 114     /* we could create a second info struct here (end_info), but it's only
 115      * useful if we want to keep pre- and post-IDAT chunk info separated
 116      * (mainly for PNG-aware image editors and converters) */
 117
 118
 119     /* setjmp() must be called in every function that calls a PNG-reading
 120      * libpng function */
 121
 122     if (setjmp(png_jmpbuf(png_ptr))) {
 123         png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
 124         return 2;
 125     }
 126
 127
 128     png_init_io(png_ptr, infile);
 129     png_set_sig_bytes(png_ptr, 8);  /* we already read the 8 signature bytes */
 130
 131     png_read_info(png_ptr, info_ptr);  /* read all PNG info up to image data */
 132
 133
 134     /* alternatively, could make separate calls to png_get_image_width(),
 135      * etc., but want bit_depth and color_type for later [don't care about
 136      * compression_type and filter_type => NULLs] */
 137
 138     png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
 139       NULL, NULL, NULL);
 140     *pWidth = width;
 141     *pHeight = height;
 142
 143
 144     /* OK, that's all we need for now; return happy */
 145
 146     return 0;
 147 }
 148
 149
 150
 151
 152 /* returns 0 if succeeds, 1 if fails due to no bKGD chunk, 2 if libpng error;
 153  * scales values to 8-bit if necessary */
 154
 155 int readpng_get_bgcolor(uch *red, uch *green, uch *blue)
 156 {
 157     png_color_16p pBackground;
 158
 159
 160     /* setjmp() must be called in every function that calls a PNG-reading
 161      * libpng function */
 162
 163     if (setjmp(png_jmpbuf(png_ptr))) {
 164         png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
 165         return 2;
 166     }
 167
 168
 169     if (!png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD))
 170         return 1;
 171
 172     /* it is not obvious from the libpng documentation, but this function
 173      * takes a pointer to a pointer, and it always returns valid red, green
 174      * and blue values, regardless of color_type: */
 175
 176     png_get_bKGD(png_ptr, info_ptr, &pBackground);
 177
 178
 179     /* however, it always returns the raw bKGD data, regardless of any
 180      * bit-depth transformations, so check depth and adjust if necessary */
 181
 182     if (bit_depth == 16) {
 183         *red   = pBackground->red   >> 8;
 184         *green = pBackground->green >> 8;
 185         *blue  = pBackground->blue  >> 8;
 186     } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
 187         if (bit_depth == 1)
 188             *red = *green = *blue = pBackground->gray? 255 : 0;
 189         else if (bit_depth == 2)
 190             *red = *green = *blue = (255/3) * pBackground->gray;
 191         else /* bit_depth == 4 */
 192             *red = *green = *blue = (255/15) * pBackground->gray;
 193     } else {
 194         *red   = (uch)pBackground->red;
 195         *green = (uch)pBackground->green;
 196         *blue  = (uch)pBackground->blue;
 197     }
 198
 199     return 0;
 200 }
 201
 202
 203
 204
 205 /* display_exponent == LUT_exponent * CRT_exponent */
 206
 207 uch *readpng_get_image(double display_exponent, int *pChannels, ulg *pRowbytes)
 208 {
 209     double  gamma;
 210     png_uint_32  i, rowbytes;
 211     png_bytepp  row_pointers = NULL;
 212
 213
 214     /* setjmp() must be called in every function that calls a PNG-reading
 215      * libpng function */
 216
 217     if (setjmp(png_jmpbuf(png_ptr))) {
 218         free(image_data);
 219         image_data = NULL;
 220         free(row_pointers);
 221         row_pointers = NULL;
 222         png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
 223         return NULL;
 224     }
 225
 226
 227     /* expand palette images to RGB, low-bit-depth grayscale images to 8 bits,
 228      * transparency chunks to full alpha channel; strip 16-bit-per-sample
 229      * images to 8 bits per sample; and convert grayscale to RGB[A] */
 230
 231     if (color_type == PNG_COLOR_TYPE_PALETTE)
 232         png_set_expand(png_ptr);
 233     if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
 234         png_set_expand(png_ptr);
 235     if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
 236         png_set_expand(png_ptr);
 237 #ifdef PNG_READ_16_TO_8_SUPPORTED
 238     if (bit_depth == 16)
 239 #  ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
 240         png_set_scale_16(png_ptr);
 241 #  else
 242         png_set_strip_16(png_ptr);
 243 #  endif
 244 #endif
 245     if (color_type == PNG_COLOR_TYPE_GRAY ||
 246         color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
 247         png_set_gray_to_rgb(png_ptr);
 248
 249
 250     /* unlike the example in the libpng documentation, we have *no* idea where
 251      * this file may have come from--so if it doesn't have a file gamma, don't
 252      * do any correction ("do no harm") */
 253
 254     if (png_get_gAMA(png_ptr, info_ptr, &gamma))
 255         png_set_gamma(png_ptr, display_exponent, gamma);
 256
 257
 258     /* all transformations have been registered; now update info_ptr data,
 259      * get rowbytes and channels, and allocate image memory */
 260
 261     png_read_update_info(png_ptr, info_ptr);
 262
 263     *pRowbytes = rowbytes = png_get_rowbytes(png_ptr, info_ptr);
 264     *pChannels = (int)png_get_channels(png_ptr, info_ptr);
 265
 266     if ((image_data = (uch *)malloc(rowbytes*height)) == NULL) {
 267         png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
 268         return NULL;
 269     }
 270     if ((row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep))) == NULL) {
 271         png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
 272         free(image_data);
 273         image_data = NULL;
 274         return NULL;
 275     }
 276
 277     Trace((stderr, "readpng_get_image:  channels = %d, rowbytes = %ld, height = %ld\n",
 278         *pChannels, rowbytes, height));
 279
 280
 281     /* set the individual row_pointers to point at the correct offsets */
 282
 283     for (i = 0;  i < height;  ++i)
 284         row_pointers[i] = image_data + i*rowbytes;
 285
 286
 287     /* now we can go ahead and just read the whole image */
 288
 289     png_read_image(png_ptr, row_pointers);
 290
 291
 292     /* and we're done!  (png_read_end() can be omitted if no processing of
 293      * post-IDAT text/time/etc. is desired) */
 294
 295     free(row_pointers);
 296     row_pointers = NULL;
 297
 298     png_read_end(png_ptr, NULL);
 299
 300     return image_data;
 301 }
 302
 303
 304 void readpng_cleanup(int free_image_data)
 305 {
 306     if (free_image_data && image_data) {
 307         free(image_data);
 308         image_data = NULL;
 309     }
 310
 311     if (png_ptr && info_ptr) {
 312         png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
 313         png_ptr = NULL;
 314         info_ptr = NULL;
 315     }
 316 }