pngtopng.c revision 9b1fe63dcc7ba076b9730b7bfa031cc0dbc25561 
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#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && \
24    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
25
26int main(int argc, const char **argv)
27{
28   int result = 1;
29
30   if (argc == 3)
31   {
32      png_image image;
33
34      /* Only the image structure version number needs to be set. */
35      memset(&image, 0, sizeof image);
36      image.version = PNG_IMAGE_VERSION;
37
38      if (png_image_begin_read_from_file(&image, argv[1]))
39      {
40         png_bytep buffer;
41
42         /* Change this to try different formats!  If you set a colormap format
43          * then you must also supply a colormap below.
44          */
45         image.format = PNG_FORMAT_RGBA;
46
47         buffer = malloc(PNG_IMAGE_SIZE(image));
48
49         if (buffer != NULL)
50         {
51            if (png_image_finish_read(&image, NULL/*background*/, buffer,
52               0/*row_stride*/, NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP */))
53            {
54               if (png_image_write_to_file(&image, argv[2],
55                  0/*convert_to_8bit*/, buffer, 0/*row_stride*/,
56                  NULL/*colormap*/))
57                  result = 0;
58
59               else
60                  fprintf(stderr, "pngtopng: write %s: %s\n", argv[2],
61                      image.message);
62
63               free(buffer);
64            }
65
66            else
67            {
68               fprintf(stderr, "pngtopng: read %s: %s\n", argv[1],
69                   image.message);
70
71               /* This is the only place where a 'free' is required; libpng does
72                * the cleanup on error and success, but in this case we couldn't
73                * complete the read because of running out of memory.
74                */
75               png_image_free(&image);
76            }
77         }
78
79         else
80            fprintf(stderr, "pngtopng: out of memory: %lu bytes\n",
81               (unsigned long)PNG_IMAGE_SIZE(image));
82      }
83
84      else
85         /* Failed to read the first argument: */
86         fprintf(stderr, "pngtopng: %s: %s\n", argv[1], image.message);
87   }
88
89   else
90      /* Wrong number of arguments */
91      fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
92
93   return result;
94}
95#endif /* READ && WRITE */
96