Using a PRNG to hash integers

gistfile1.c

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

int const WIDTH = 512;
int const HEIGHT = 512;

int main(int argc, char *argv[])
{
    /* Pass the seed as the first argument */
    int seed = argc > 1 ? atoi(argv[1]) : 0;
    int x, y, tmp;

    printf("P2\n");
    printf("# Test image\n");
    printf("%d %d\n", WIDTH, HEIGHT);
    printf("255\n");
    for (y = 0; y < HEIGHT; ++y)
    {
        for (x = 0; x < WIDTH; ++x)
        {
            srand(seed); tmp = rand();
            srand(tmp + x); tmp = rand();
            srand(tmp + y); tmp = rand();

            printf("%d ", (int)(tmp * 255.f / RAND_MAX));
        }
        printf("\n");
    }
}