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