circle.ts

import { asInt } from "@thi.ng/api/typedarray";
import { clipped, intersectRectCircle } from "./clipping.js";
import { hline } from "./hvline.js";

export function* circle(cx: number, cy: number, r: number, fill = true) {
	[cx, cy, r] = asInt(cx, cy, r);
	if (r < 1) return;
	let x = 0;
	let y = r;
	let y2 = r * r;
	let sum = y2 + r;
	let dx2 = 1;
	let dy2 = 2 * r - 1;

	while (x <= y) {
		if (fill) {
			yield* hline(cx - y, cy + x, y << 1);
			if (x) yield* hline(cx - y, cy - x, y << 1);
		} else {
			yield [cx - y, cy + x];
			if (y) yield [cx + y, cy + x];
			if (x) {
				yield [cx - y, cy - x];
				if (y) yield [cx + y, cy - x];
			}
			if (x !== y) {
				yield [cx - x, cy - y];
				if (x) yield [cx + x, cy - y];
				if (y) {
					yield [cx - x, cy + y];
					if (x) yield [cx + x, cy + y];
				}
			}
		}
		sum -= dx2;
		if (sum <= y2) {
			if (fill && x !== y) {
				yield* hline(cx - x, cy - y, x << 1);
				if (y) yield* hline(cx - x, cy + y, x << 1);
			}
			y--;
			y2 -= dy2;
			dy2 -= 2;
		}
		x++;
		dx2 += 2;
	}
}

/**
 * Version of {@link circle} yielding only coordinates in rect defined by
 * `left,top`..`right,bottom`. Returns undefined if circle lies completely
 * outside given clip rectangle.
 *
 * @param cx -
 * @param cy -
 * @param r -
 * @param left -
 * @param top -
 * @param right -
 * @param bottom -
 * @param fill -
 */
export const circleClipped = (
	cx: number,
	cy: number,
	r: number,
	left: number,
	top: number,
	right: number,
	bottom: number,
	fill = true
) => {
	return intersectRectCircle(left, top, right, bottom, cx, cy, r)
		? clipped(circle(cx, cy, r, fill), left, top, right, bottom)
		: undefined;
};