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

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

   http://www.ijg.org/
   http://en.wikipedia.org/wiki/JPEG#Syntax_and_structure
   http://www.media.mit.edu/pia/Research/deepview/exif.html

   2013-04-20
                                                                           */

#include<stdio.h>

#define SHOW_MARKERS 0

static void GetFileSize(FILE *file, int *width, int *height)
{
   unsigned char buffer[8];
   int i;

   *width = *height = 0;

   /* Check SOI marker */
   if( fread(buffer, 2, 1, file) != 1 ||
       buffer[0] != 0xff || buffer[1] != 0xd8 )
   {
      return;
   }

   for(;;)
   {
      /* Skip markers until we get a SOF marker */
      do
      {
         if( (i = fgetc(file)) == EOF )
            return;
      } while( i != 0xff );

      /* Got the first byte (0xff) of segment, read second marker byte
         and payload.

         buffer[0] = marker byte
         buffer[1..2] = length
         buffer[3..7] = next 5 bytes of payload                        */
      if( fread(buffer, 8, 1, file) != 1 )
         return;
      if( buffer[0] >= 0xc0 && buffer[0] <= 0xcf && buffer[0] != 0xc4 )
      {
         /* Found a SOF marker */
         #if SHOW_MARKERS
            fprintf(stderr, "ff %02x: width=%02x%02x height=%02x%02x\n",
                    buffer[0], buffer[4], buffer[5], buffer[6], buffer[7]);
         #endif
         *height = (buffer[4] << 8) | buffer[5];
         *width = (buffer[6] << 8) | buffer[7];
         return;
      }

      /* Skip over this segment.  Bytes 1..2 contains the payload length,
         which will be adjusted for the 7 bytes we already read.          */
      #if SHOW_MARKERS
         fprintf(stderr, "ff %02x: length=%02x%02x\n",
                 buffer[0], buffer[1], buffer[2]);
      #endif
      for(i = ((buffer[1] << 8) | buffer[2]) - 7; i > 0; i--)
      {
         if( fgetc(file) == EOF )
            return;
      }
   }
}

int main(int argc, char **argv)
{
   int width, height;
   GetFileSize(stdin, &width, &height);
   printf("%d %d\n", width, height);
   return 0;
}