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
24int 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}