kc3-lang/libpng/contrib/examples/pngtopng.c

Branch - branch -libpng16libpng17

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• Hash : 3bca02e2
  Author :
  Date : 2025-06-01T22:40:38
  

  examples: Refactor and reformat using clang-format
  
  Add contrib/examples/.clang-format, tailored to fit the existing code
  as closely as possible. The end goal is to set up automatic formatting
  for the entire libpng source tree. We're doing this experiment in this
  subdirectory, for now.
  
  Also make refactoring changes, as follows:
  
   * Rewrite the preprocessor checks `#if PNG_FOO_SUPPORTED` to stop
     compilation immediately, with a descriptive `#error` about what
     needs to be supported.
  
   * Rewrite and reflow comments, add braces and brackets, and make other
     minor modifications that are suited for the clang-format'ed code.
  

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• contrib/examples/pngtopng.c

• /*- pngtopng
   *
   * COPYRIGHT: Written by John Cunningham Bowler, 2011, 2017.
   * To the extent possible under law, the author has waived all copyright and
   * related or neighboring rights to this work.  This work is published from:
   * United States.
   *
   * Read a PNG and write it out in a fixed format, using the 'simplified API'
   * that was introduced in libpng-1.6.0.
   *
   * This sample code is just the code from 'example.c' with some error handling
   * added.  See example.c in the top-level libpng directory for more comments.
   */
  #include <stddef.h>
  #include <stdlib.h>
  #include <string.h>
  #include <stdio.h>
  
  /* Normally use <png.h> here to get the installed libpng, but this is done to
   * ensure the code picks up the local libpng implementation:
   */
  #include "../../png.h"
  
  #if !defined(PNG_SIMPLIFIED_READ_SUPPORTED) || \
      !defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
  #error This program requires libpng supporting the simplified read/write API
  #endif
  
  
  int
  main(int argc, const char **argv)
  {
     int result = 1;
  
     if (argc == 3)
     {
        png_image image;
  
        /* Only the image structure version number needs to be set. */
        memset(&image, 0, sizeof image);
        image.version = PNG_IMAGE_VERSION;
  
        if (png_image_begin_read_from_file(&image, argv[1]))
        {
           png_bytep buffer;
  
           /* Change this to try different formats!  If you set a colormap format
            * then you must also supply a colormap below.
            */
           image.format = PNG_FORMAT_RGBA;
  
           buffer = malloc(PNG_IMAGE_SIZE(image));
  
           if (buffer != NULL)
           {
              if (png_image_finish_read(&image, NULL /*background*/, buffer,
                                        0 /*row_stride*/, NULL /*colormap */))
              {
                 if (png_image_write_to_file(
                        &image, argv[2], 0 /*convert_to_8bit*/, buffer,
                        0 /*row_stride*/, NULL /*colormap*/))
                    result = 0;
  
                 else
                    fprintf(stderr, "pngtopng: write %s: %s\n", argv[2],
                            image.message);
              }
  
              else
                 fprintf(stderr, "pngtopng: read %s: %s\n", argv[1],
                         image.message);
  
              free(buffer);
           }
  
           else
           {
              fprintf(stderr, "pngtopng: out of memory: %lu bytes\n",
                      (unsigned long)PNG_IMAGE_SIZE(image));
  
              /* This is the only place where a 'free' is required; libpng does
               * the cleanup on error and success, but in this case we couldn't
               * complete the read because of running out of memory and so libpng
               * has not got to the point where it can do cleanup.
               */
              png_image_free(&image);
           }
        }
  
        else
           /* Failed to read the first argument: */
           fprintf(stderr, "pngtopng: %s: %s\n", argv[1], image.message);
     }
  
     else
        /* Wrong number of arguments */
        fprintf(stderr, "pngtopng: usage: pngtopng input-file output-file\n");
  
     return result;
  }
  

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