code/x11-random/worley-noise.c

#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <math.h>

#define WIDTH 1280
#define HEIGHT 720
#define SEED 1234567

#define POINTS 20

static int seed_offset = 1;

struct point {
	int x;
	int y;
};


double dist_p1_p2(int p1x, int p1y, int p2x, int p2y)
{
	double pA, pB;
	pA = p1x - p2x;
	pB = p1y - p2y;

	return sqrt(pA * pA + pB * pB);

}

void draw_pixel(Display * di, Window wi, GC gc, int x, int y, int color)
{
	XSetForeground(di, gc, color);
	XDrawPoint(di, wi, gc, x, y);
}

float rand_0_1()
{
	srand48(SEED + seed_offset++);
	return drand48();
}

void sort(double *arr)
{
	int arr_size = POINTS;
	int i, j, aux;
	for (i = 0; i < arr_size; i++) {
		for (j = i + 1; j < arr_size; j++) {
			if (arr[i] > arr[j]) {
				aux = arr[j];
				arr[j] = arr[i];
				arr[i] = aux;
			}
		}
	}

}

int map(int value, int min, int max, int map_min, int map_max)
{
	double R = (double) (map_max - map_min) / (double) (max - min);
	double y = map_min + (value * R) + R;
	return (int) y;
}

void worley_noise(Display * di, Window wi, GC gc)
{
	int x, y, i;
	int c;
	int noise_space[WIDTH][HEIGHT];
	double dist[POINTS], sdist[POINTS];
	struct point p[POINTS];


	for (x = 0; x < WIDTH; x++) {
		for (y = 0; y < HEIGHT; y++) {
			c = (int) (rand_0_1() * 255);
			c = (c << 16) | (c << 8) | c;
			noise_space[x][y] = c;
		}
	}

	for (i = 0; i < POINTS; i++) {
		p[i].x = (int) (rand_0_1() * WIDTH);
		p[i].y = (int) (rand_0_1() * HEIGHT);
	}
	for (x = 0; x < WIDTH; x++) {
		for (y = 0; y < HEIGHT; y++) {
			for (i = 0; i < POINTS; i++) {
				dist[i] = dist_p1_p2(x, y, p[i].x, p[i].y);
				sort(dist);
			}
			c = map(dist[0], 0, WIDTH / 4, 255, 20);

			c = (c << 16) | (c << 8) | c;
			draw_pixel(di, wi, gc, x, y, c);
		}
	}
}

int main()
{
	Display *di = XOpenDisplay(getenv("DISPLAY"));
	if (di == NULL) {
		fprintf(stderr, "ERROR: No display");
		exit(EXIT_FAILURE);
	}
	int x = 0, y = 0, width = WIDTH, height = HEIGHT, border_width = 1;
	int sc = DefaultScreen(di);
	Window ro = DefaultRootWindow(di);
	Window wi = XCreateSimpleWindow(di,
					ro,
					x,
					y,
					width,
					height,
					border_width,
					BlackPixel(di, sc),
					WhitePixel(di, sc));

	XMapWindow(di, wi);
	XStoreName(di, wi, "Default Window");

	GC gc = XCreateGC(di, ro, 0, NULL);

	XSelectInput(di, wi, KeyPressMask | ExposureMask);
	XEvent ev;
	int quit = 0;
	int z = 50;
	while (!quit) {
		int a = XNextEvent(di, &ev);
		if (ev.type == KeyPress) {
			printf("KeyPress %x\n", ev.xkey.keycode);
			quit = 1;
		}
		if (ev.type == Expose) {
			worley_noise(di, wi, gc);
		}
	}

	XFreeGC(di, gc);
	XDestroyWindow(di, wi);
	XCloseDisplay(di);
	return (EXIT_SUCCESS);

}