calculer la taille d'une image jpg

#include <stdio.h>

void main (int argc, char *argv[])
{
int k;
char fichier[50],IN[255];
unsigned char buf[7], jfif[5];
FILE *in, *out;
char w=0,h=0,w1=0,h1=0;
int len =0, offset;

        if ( argc < 2 ) { printf("jpg_info <filename>\n"); exit(0);}
        sprintf(IN,"%s",argv[1]);
        if((in = fopen(IN,"rb"))== NULL){
                                    printf("Arghh...\n");
                                    exit(0);
                     }

        k = fread(buf,1,4,in); // must be FF D8 FF E0
        k = fread(&w,1,1,in);
        k = fread(&w1,1,1,in);
        len = w*256 + w1;
        k = fread(jfif,1,5,in); // must be JFIF\0x00

        offset = 2;
        buf[0] = 0xFF; buf[1] = 0xFF;

        while ( buf[0] != 0xFF ||
                               !( buf[1] == 0xC0 ||
                               buf[1] == 0xC2 ) ) {
          offset += len +2;
          fseek(in, offset, SEEK_SET );
          fread(buf,1,2,in);
          k = fread(&w,1,1,in);
          k = fread(&w1,1,1,in);
          len = w*256 + w1;
        }
        k = fread(buf,1,1,in);
        k = fread(&h,1,1,in);
        k = fread(&h1,1,1,in);
        k = fread(&w,1,1,in);
        k = fread(&w1,1,1,in);
        printf("width=\"%d\" height=\"%d\"\n",w*256+w1,h*256+h1);
        fclose(in);
}