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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 #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 */
     96