ft, e.clientY - canvas_rect.top];
		if(document.getElementById("i_1").checked) { // add
			points_for_interpolation.push(xy);
			interpolation_i = points_for_interpolation.length-1;
		} else { // move
			interpolation_i = nearest_i(xy, points_for_interpolation);
			points_for_interpolation[interpolation_i] = xy;
		}
		draw_canvas("interpolation_canvas");
		canvas.releasePointerCapture(e.pointerId);
	}, false);

	canvas.addEventListener('pointermove', function(e){
		if(e.buttons == 1){
			canvas_rect = canva