#include <u.h>
#include <libc.h>
#include <draw.h>
Image *px;
uchar sq[128*128];
uchar bayer[8][8] = {
	{0, 128, 32, 160, 8, 136, 40, 168},
	{192, 64, 224, 96, 200, 72, 232, 104},
	{48, 176, 16, 144, 56, 184, 24, 152},
	{240, 112, 208, 80, 248, 120, 216, 88},
	{12, 140, 44, 172, 4, 132, 36, 164},
	{204, 76, 236, 108, 196, 68, 228, 100},
	{60, 188, 28, 156, 52, 180, 20, 148},
	{252, 124, 220, 92, 244, 116, 212, 84}
};
void
dither(void){
	Rectangle r;
	int x, y;
	uchar p;
	r.min.y = screen->r.min.y;
	for(y = 0; y < 128; y++){
		r.max.y = r.min.y + 4;
		r.min.x = screen->r.min.x;
		for(x = 0; x < 128; x++){
			r.max.x = r.min.x + 4;
			p = 255 + (sq[y << 7 | x] < bayer[x & 7][y & 7]);
			loadimage(px, px->r, &p, 1);
			draw(screen, r, px, nil, ZP);
			flushimage(display, 1);
			sleep(1);
			r.min.x = r.max.x;
		}
		r.min.y = r.max.y;
	}
}
void
sillywalk(int n, float d){
	Rectangle r;
	int c;
	if(sq[n])
		return;
	sq[n] = 255.0 * (sin(d) * 0.5 + 0.5);
	loadimage(px, px->r, sq + n, 1);
	r = rectaddpt(Rect(0, 0, 4, 4), screen->r.min);
	r = rectaddpt(r, Pt(n << 2 & 508,  n >> 5 & 508));
	draw(screen, r, px, nil, ZP);
	flushimage(display, 1);
	sleep(1);
	c = 0;
	switch(lrand() & 3){
	case 0: again:
		sillywalk(n - 128 & 16383, d + 0.01);
		if(++c == 4)
			break;
	case 1:
		sillywalk(n + 1 & 16383, d + 0.01);
		if(++c == 4)
			break;
	case 2:
		sillywalk(n + 128 & 16383, d + 0.01);
		if(++c == 4)
			break;
	case 3:
		sillywalk(n - 1 & 16383, d + 0.01);
		if(++c == 4)
			break;
		goto again;
	}
}
void
main(int, char**){
	ulong i;
	i = truerand();
	print("0x%.8ux\n", i);
	srand(i);
	if(initdraw(nil, nil, "bayer walk") < 0)
		sysfatal("initdraw: %r");
	px = allocimage(display, Rect(0, 0, 1, 1), CMAP8, 1, DNofill);
	if(px == nil)
		sysfatal("allocimage: %r");
	sillywalk(lrand() & 16383, 0.01);
	dither();
	sleep(9999990);
	exits(nil);
}