text: #include <stdio.h>
  #include <stdlib.h>		/* For atoi */
  #include "gd.h"
  
  /* A short program which converts a .png file into a .gd file, for
     your convenience in creating images on the fly from a
     basis image that must be loaded quickly. The .gd format
     is not intended to be a general-purpose format. */
  
  int
  main (int argc, char **argv)
  {
    gdImagePtr im;
    FILE *in, *out;
    int x, y, w, h;
  
    if (argc != 7)
      {
        fprintf (stderr, "Usage: gdparttopng filename.gd filename.png x y w h\n");
        exit (1);
      }
    in = fopen (argv[1], "rb");
    if (!in)
      {
        fprintf (stderr, "Input file does not exist!\n");
        exit (1);
      }
  
    x = atoi (argv[3]);
    y = atoi (argv[4]);
    w = atoi (argv[5]);
    h = atoi (argv[6]);
  
    printf ("Extracting from (%d, %d), size is %dx%d\n", x, y, w, h);
  
    im = gdImageCreateFromGd2Part (in, x, y, w, h);
    fclose (in);
    if (!im)
      {
        fprintf (stderr, "Input is not in GD2 format!\n");
        exit (1);
      }
    out = fopen (argv[2], "wb");
    if (!out)
      {
        fprintf (stderr, "Output file cannot be written to!\n");
        gdImageDestroy (im);
        exit (1);
      }
  #ifdef HAVE_LIBPNG
    gdImagePng (im, out);
  #else
    fprintf(stderr, "No PNG library support.\n");
  #endif
    fclose (out);
    gdImageDestroy (im);
  
    return 0;
  }
  