view release on metacpan or  search on metacpan

src/Source/LibPNG/example.c  view on Meta::CPAN

#if 0 /* in case someone actually tries to compile this */

/* example.c - an example of using libpng
 * Last changed in libpng 1.6.15 [November 20, 2014]
 * Maintained 1998-2014 Glenn Randers-Pehrson
 * Maintained 1996, 1997 Andreas Dilger)
 * Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 * To the extent possible under law, the authors have waived
 * all copyright and related or neighboring rights to this file.
 * This work is published from: United States.
 */

/* This is an example of how to use libpng to read and write PNG files.
 * The file libpng-manual.txt is much more verbose then this.  If you have not
 * read it, do so first.  This was designed to be a starting point of an
 * implementation.  This is not officially part of libpng, is hereby placed
 * in the public domain, and therefore does not require a copyright notice.
 *
 * This file does not currently compile, because it is missing certain
 * parts, like allocating memory to hold an image.  You will have to
 * supply these parts to get it to compile.  For an example of a minimal
 * working PNG reader/writer, see pngtest.c, included in this distribution;
 * see also the programs in the contrib directory.
 */

/* The simple, but restricted, approach to reading a PNG file or data stream
 * just requires two function calls, as in the following complete program.
 * Writing a file just needs one function call, so long as the data has an
 * appropriate layout.
 *
 * The following code reads PNG image data from a file and writes it, in a
 * potentially new format, to a new file.  While this code will compile there is
 * minimal (insufficient) error checking; for a more realistic version look at
 * contrib/examples/pngtopng.c
 */
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <png.h>
#include <zlib.h>

int main(int argc, const char **argv)
{
   if (argc == 3)
   {
      png_image image; /* The control structure used by libpng */

      /* Initialize the 'png_image' structure. */
      memset(&image, 0, (sizeof image));
      image.version = PNG_IMAGE_VERSION;

      /* The first argument is the file to read: */
      if (png_image_begin_read_from_file(&image, argv[1]) != 0)
      {
         png_bytep buffer;

         /* Set the format in which to read the PNG file; this code chooses a
          * simple sRGB format with a non-associated alpha channel, adequate to
          * store most images.
          */
         image.format = PNG_FORMAT_RGBA;

         /* Now allocate enough memory to hold the image in this format; the
          * PNG_IMAGE_SIZE macro uses the information about the image (width,
          * height and format) stored in 'image'.
          */
         buffer = malloc(PNG_IMAGE_SIZE(image));

         /* If enough memory was available read the image in the desired format
          * then write the result out to the new file.  'background' is not
          * necessary when reading the image because the alpha channel is
          * preserved; if it were to be removed, for example if we requested