function hue2rgb(p, q, t) {
			if(t < 0) t += 1;
			if(t > 1) t -= 1;
			if(t < 1/6) return p + (q - p) * 6 * t;
			if(t < 1/2) return q;
			if(t < 2/3) return p + (q - p) * (2/3 - t) * 6;
			return p;
		}
Drawing handling, with mouse or touch