#include "image.h"
#include <memdraw.h>

enum {
	Empty = DWhite
};

int
isempty(Memimage *mem, Point p)
{
	if(!ptinrect(p, mem->r) || BGLONG(byteaddr(mem, p)) == Empty)
		return 1;
	return 0;
}

void
usage(void)
{
	fprint(2, "usage: %s\n", argv0);
	exits("usage");
}

void
main(int argc, char **argv)
{
	Memimage *srcmem, *dstmem;
	int y, x;
	uchar *src, *dst;

	ARGBEGIN {
	default:
		usage();
	} ARGEND

	memimageinit();

	if((srcmem = readmemimage(0)) == nil)
		sysfatal("read image: %r");
	if(srcmem->chan != RGBA32)
		sysfatal("not RGBA32");

	if((dstmem = allocmemimage(srcmem->r, srcmem->chan)) == nil)
		sysfatal("alloc dstmem: %r");

	for(y = srcmem->r.min.y; y < srcmem->r.max.y; y++) {
		for(x = srcmem->r.min.x; x < srcmem->r.max.x; x++) {
			src = byteaddr(srcmem, Pt(x, y));
			dst = byteaddr(dstmem, Pt(x, y));
			BPLONG(dst, Empty);
			if(BGLONG(src) == Empty)
				continue;

			if(isempty(srcmem, Pt(x-1, y)))
				BPLONG(dst, DRed);

			if(isempty(srcmem, Pt(x+1, y)))
				BPLONG(dst, DBlue);

			if(isempty(srcmem, Pt(x, y-1)))
				BPLONG(dst, DGreen);

			if(isempty(srcmem, Pt(x, y+1)))
				BPLONG(dst, DYellow);
		}
	}

	if(writememimage(1, dstmem) < 0)
		sysfatal("write image: %r");

	exits(nil);
}