/**
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* Catmull-Rom spline 插值折线
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* @module zrender/shape/util/smoothSpline
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* @author pissang (https://www.github.com/pissang)
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* Kener (@Kener-林峰, kener.linfeng@gmail.com)
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* errorrik (errorrik@gmail.com)
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*/
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import {distance as v2Distance} from '../../core/vector';
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/**
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* @inner
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*/
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function interpolate(p0, p1, p2, p3, t, t2, t3) {
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var v0 = (p2 - p0) * 0.5;
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var v1 = (p3 - p1) * 0.5;
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return (2 * (p1 - p2) + v0 + v1) * t3
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+ (-3 * (p1 - p2) - 2 * v0 - v1) * t2
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+ v0 * t + p1;
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}
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/**
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* @alias module:zrender/shape/util/smoothSpline
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* @param {Array} points 线段顶点数组
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* @param {boolean} isLoop
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* @return {Array}
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*/
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export default function (points, isLoop) {
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var len = points.length;
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var ret = [];
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var distance = 0;
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for (var i = 1; i < len; i++) {
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distance += v2Distance(points[i - 1], points[i]);
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}
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var segs = distance / 2;
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segs = segs < len ? len : segs;
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for (var i = 0; i < segs; i++) {
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var pos = i / (segs - 1) * (isLoop ? len : len - 1);
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var idx = Math.floor(pos);
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var w = pos - idx;
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var p0;
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var p1 = points[idx % len];
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var p2;
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var p3;
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if (!isLoop) {
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p0 = points[idx === 0 ? idx : idx - 1];
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p2 = points[idx > len - 2 ? len - 1 : idx + 1];
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p3 = points[idx > len - 3 ? len - 1 : idx + 2];
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}
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else {
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p0 = points[(idx - 1 + len) % len];
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p2 = points[(idx + 1) % len];
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p3 = points[(idx + 2) % len];
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}
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var w2 = w * w;
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var w3 = w * w2;
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ret.push([
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interpolate(p0[0], p1[0], p2[0], p3[0], w, w2, w3),
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interpolate(p0[1], p1[1], p2[1], p3[1], w, w2, w3)
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]);
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}
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return ret;
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}
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