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      1 /*- pngtopng
      2  *
      3  * COPYRIGHT: Written by John Cunningham Bowler, 2011, 2017.
      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  * Last changed in libpng 1.6.29 [March 16, 2017]
      9  *
     10  * Read a PNG and write it out in a fixed format, using the 'simplified API'
     11  * that was introduced in libpng-1.6.0.
     12  *
     13  * This sample code is just the code from the top of 'example.c' with some error
     14  * handling added.  See example.c for more comments.
     15  */
     16 #include <stddef.h>
     17 #include <stdlib.h>
     18 #include <string.h>
     19 #include <stdio.h>
     20 
     21 /* Normally use <png.h> here to get the installed libpng, but this is done to
     22  * ensure the code picks up the local libpng implementation:
     23  */
     24 #include "../../png.h"
     25 #if defined(PNG_SIMPLIFIED_READ_SUPPORTED) && \
     26     defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
     27 
     28 int main(int argc, const char **argv)
     29 {
     30    int result = 1;
     31 
     32    if (argc == 3)
     33    {
     34       png_image image;
     35 
     36       /* Only the image structure version number needs to be set. */
     37       memset(&image, 0, sizeof image);
     38       image.version = PNG_IMAGE_VERSION;
     39 
     40       if (png_image_begin_read_from_file(&image, argv[1]))
     41       {
     42          png_bytep buffer;
     43 
     44          /* Change this to try different formats!  If you set a colormap format
     45           * then you must also supply a colormap below.
     46           */
     47          image.format = PNG_FORMAT_RGBA;
     48 
     49          buffer = malloc(PNG_IMAGE_SIZE(image));
     50 
     51          if (buffer != NULL)
     52          {
     53             if (png_image_finish_read(&image, NULL/*background*/, buffer,
     54                0/*row_stride*/, NULL/*colormap for PNG_FORMAT_FLAG_COLORMAP */))
     55             {
     56                if (png_image_write_to_file(&image, argv[2],
     57                   0/*convert_to_8bit*/, buffer, 0/*row_stride*/,
     58                   NULL/*colormap*/))
     59                   result = 0;
     60 
     61                else
     62                   fprintf(stderr, "pngtopng: write %s: %s\n", argv[2],
     63                       image.message);
     64             }
     65 
     66             else
     67                fprintf(stderr, "pngtopng: read %s: %s\n", argv[1],
     68                    image.message);
     69 
     70             free(buffer);
     71          }
     72 
     73          else
     74          {
     75             fprintf(stderr, "pngtopng: out of memory: %lu bytes\n",
     76                (unsigned long)PNG_IMAGE_SIZE(image));
     77 
     78             /* This is the only place where a 'free' is required; libpng does
     79              * the cleanup on error and success, but in this case we couldn't
     80              * complete the read because of running out of memory and so libpng
     81              * has not got to the point where it can do cleanup.
     82              */
     83             png_image_free(&image);
     84          }
     85       }
     86 
     87       else
     88          /* Failed to read the first argument: */
     89          fprintf(stderr, "pngtopng: %s: %s\n", argv[1], image.message);
     90    }
     91 
     92    else
     93       /* Wrong number of arguments */
     94       fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
     95 
     96    return result;
     97 }
     98 #endif /* READ && WRITE */
     99