gistfile1.txt

f = fopen (filename, "ab");       /* reopen in binary append mode */
     for (y = height - 1; y >= 0; y--)
       {
         for (x = 0; x < width; x++)
           {
             i = (y * width + x) * 4;
             printf ("i is now: %i\n", i);
             if (ptr != 0)
               {
                 fputc (ptr[i + 2], f);        /* write blue */
                 fputc (ptr[i + 1], f);        /* write green */
                 fputc (ptr[i], f);    /* write red */
               }
           }
       }
     fclose (f);