#include <stdio.h>
#include <stdlib.h>
#include <time.h>

/* Induce simulated CCD noise in a PNM image. Written to make a static image
 * look like a webcam (some friends and I built a fake machine-room-cam page as
 * a joke in my first year). */

int main(int argc, char **argv) {
	int w, h, max, i, range;

	range = (argc < 2) ? 20 : atoi(argv[1]);

	srand(time(NULL));

	scanf("P6\n");
	scanf("%d %d\n", &w, &h);
	scanf("%d", &max);
	fgetc(stdin); /* get the last whitespace char */
	if (max > 255) exit(20);

	printf("P6\n%d %d\n%d\n", w, h, max);

	for (i = 0; i < w * h * 3; i++) {
		int val = fgetc(stdin);
		int rndnum = rand() % range;
		if (rand() % 2) {
			if (val < 255-rndnum) val += rndnum;
		} else {
			if (val > rndnum) val -= rndnum;
		}
		fputc(val, stdout);
	}

	return 0;
}