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   * 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  
      64              else
      65                 fprintf(stderr, "pngtopng: read %s: %s\n", argv[1],
      66                     image.message);
      67  
      68              free(buffer);
      69           }
      70  
      71           else
      72           {
      73              fprintf(stderr, "pngtopng: out of memory: %lu bytes\n",
      74                 (unsigned long)PNG_IMAGE_SIZE(image));
      75  
      76              /* This is the only place where a 'free' is required; libpng does
      77               * the cleanup on error and success, but in this case we couldn't
      78               * complete the read because of running out of memory and so libpng
      79               * has not got to the point where it can do cleanup.
      80               */
      81              png_image_free(&image);
      82           }
      83        }
      84  
      85        else
      86           /* Failed to read the first argument: */
      87           fprintf(stderr, "pngtopng: %s: %s\n", argv[1], image.message);
      88     }
      89  
      90     else
      91        /* Wrong number of arguments */
      92        fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
      93  
      94     return result;
      95  }
      96  #endif /* READ && WRITE */