source/libs/libpng/libpng-src/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 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && \
  24     defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
  25
  26 int 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 */