share/png/contrib/examples/pngtopng.c

   1 /*- pngtopng
   2  *
   3  * COPYRIGHT: Written by John Cunningham Bowler, 2011.
   4  * To the extent possible under law, the author has waived all copyright and
   5  * related or neighboring rights to this work.  This work is published from:
   6  * United States.
   7  *
   8  * Read a PNG and write it out in a fixed format, using the 'simplified API'
   9  * that was introduced in libpng-1.6.0.
  10  *
  11  * This sample code is just the code from the top of 'example.c' with some error
  12  * handling added.  See example.c for more comments.
  13  */
  14 #include <stddef.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <stdio.h>
  18
  19 /* Normally use <png.h> here to get the installed libpng, but this is done to
  20  * ensure the code picks up the local libpng implementation:
  21  */
  22 #include "../../png.h"
  23
  24 int main(int argc, const char **argv)
  25 {
  26    int result = 1;
  27
  28    if (argc == 3)
  29    {
  30       png_image image;
  31
  32       /* Only the image structure version number needs to be set. */
  33       memset(&image, 0, sizeof image);
  34       image.version = PNG_IMAGE_VERSION;
  35
  36       if (png_image_begin_read_from_file(&image, argv[1]))
  37       {
  38          png_bytep buffer;
  39
  40          /* Change this to try different formats!  If you set a colormap format
  41           * then you must also supply a colormap below.
  42           */
  43          image.format = PNG_FORMAT_RGBA;
  44
  45          buffer = malloc(PNG_IMAGE_SIZE(image));
  46
  47          if (buffer != NULL)
  48          {
  49             if (png_image_finish_read(&image, NULL/*background*/, buffer,
  50                0/*row_stride*/, NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP */))
  51             {
  52                if (png_image_write_to_file(&image, argv[2],
  53                   0/*convert_to_8bit*/, buffer, 0/*row_stride*/,
  54                   NULL/*colormap*/))
  55                   result = 0;
  56
  57                else
  58                   fprintf(stderr, "pngtopng: write %s: %s\n", argv[2],
  59                       image.message);
  60
  61                free(buffer);
  62             }
  63
  64             else
  65             {
  66                fprintf(stderr, "pngtopng: read %s: %s\n", argv[1],
  67                    image.message);
  68
  69                /* This is the only place where a 'free' is required; libpng does
  70                 * the cleanup on error and success, but in this case we couldn't
  71                 * complete the read because of running out of memory.
  72                 */
  73                png_image_free(&image);
  74             }
  75          }
  76
  77          else
  78             fprintf(stderr, "pngtopng: out of memory: %lu bytes\n",
  79                (unsigned long)PNG_IMAGE_SIZE(image));
  80       }
  81
  82       else
  83          /* Failed to read the first argument: */
  84          fprintf(stderr, "pngtopng: %s: %s\n", argv[1], image.message);
  85    }
  86
  87    else
  88       /* Wrong number of arguments */
  89       fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
  90
  91    return result;
  92 }