/*

Simple steg example by lovepump, (c) 2005

*/


#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <openssl/sha.h>

#include "steg.h"

int main(int argc, char **argv) 
{

	FILE 		*in, *out;
	unsigned char 	*img, hash[20], *ct;
	unsigned long 	n, flen;
	int 		i, j, bitspixel, colmap;	
	HDR 		*header;
	
	if(argc < 4) {
		printf("Usage: %s infile outfile text\n", argv[0]);
		printf("Where text is the phrase to SHA1 hash and steg\n");
		return -1;
	}

	in = fopen(argv[1], "r");
	out = fopen(argv[2], "w+");

	fseek(in, 0, SEEK_END);
	flen = ftell(in);
	rewind(in);

	img = (char *)malloc(flen);
	header = (HDR*)img;

	fread(img, flen, 1, in);
	
	colmap = ((header->flags)>>7);
	bitspixel = ((header->flags & 7)+1);
	printf("GIF:\nWidth = %d, Height = %d\n", header->width, header->height);
	printf("Bits per pixel: %d, Colour map = %d\n", bitspixel, colmap);
	printf("Colour table size: %f bits, %f bytes.\n", pow(2,bitspixel), pow(2,bitspixel)/8);
	
	if(pow(2,bitspixel)/8 < 32) exit(-1);

	n = strlen(argv[3]);
	
	SHA1(argv[3], n, hash);

	ct = img + sizeof(header) + 7;

	for(i = 0; i < 20; i++) {
		for(j = 0; j < 8; j++) {
			*ct = (*ct & 254);
			if(hash[i] & 1) (*ct)++;
			hash[i]>>=1;
			ct++;
		}
	}		
	fwrite(img, flen, 1, out); 
	fclose(in);
	fclose(out);

	return 1;
}