/* pngsize.c - Don Yang (uguu.org)

   Reads PNG image from stdin, and writes width and height to stdout.

   http://libpng.org/pub/png/spec/iso/

   2013-04-20
                                                                           */

#include<stdio.h>
#include<string.h>

int main(int argc, char **argv)
{
   unsigned char expected_header[8] = {137, 80, 78, 71, 13, 10, 26, 10};
   unsigned char header[24];
   unsigned int width = 0, height = 0;

   if( fread(header, 24, 1, stdin) == 1 &&
       memcmp(expected_header, header, sizeof(expected_header)) == 0 )
   {
      width = (header[16] << 24) |
              (header[17] << 16) |
              (header[18] << 8) |
              header[19];
      height = (header[20] << 24) |
               (header[21] << 16) |
               (header[22] << 8) |
               header[23];
   }
   printf("%u %u\n", width, height);
   return 0;
}