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      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 }
     93