Number(document.getElementById("center_y").value);
	const scale = Number(document.getElementById("scale").value);
	const type = document.getElementById("scale_1").checked
		? LINEAR
		: ATAN;
	return s2x_x2s_s2y_y2s(type, center_x, center_y, scale);
}

var mousedown_sx;
var mousedown_sy;
var mousemove_sx;
var mousemove_sy;
function init_canvas() {
	canvas = document.getElementById("canvas");
	const canvas_rect = canvas.getBoundingClientRect();

	canvas.addEventListener('click', function(e) {
		const canvas_