paper.js/test/tests/Path_Length.js

/*
 * Paper.js - The Swiss Army Knife of Vector Graphics Scripting.
 * http://paperjs.org/
 *
 * Copyright (c) 2011 - 2016, Juerg Lehni & Jonathan Puckey
 * http://scratchdisk.com/ & http://jonathanpuckey.com/
 *
 * Distributed under the MIT license. See LICENSE file for details.
 *
 * All rights reserved.
 */

QUnit.module('Path Length');

test('path.length', function() {
    var path = new Path([
        new Segment(new Point(121, 334), new Point(-19, 38), new Point(30.7666015625, -61.53369140625)),
        new Segment(new Point(248, 320), new Point(-42, -74), new Point(42, 74))
    ]);

    var length = path.length;
    equals(length, 172.10112809179614, 'path.length');

    var param = path.curves[0].getParameterAt(length / 4);
    equals(param, 0.2255849553116685, 'path.curves[0].getParameterAt(length / 4)');
});

test('curve.getParameter with straight curve', function() {
    var path = new Path();
    path.moveTo(100, 100);
    path.lineTo(500, 500);
    var curve = path.curves[0];
    var length = curve.length;
    var t = curve.getParameterAt(length / 3);
    equals(t, 0.3869631475722452);
});