zh/builder/src/zrender3/graphic/helper/smoothBezier.js

/**
 * 贝塞尔平滑曲线
 * @module zrender/shape/util/smoothBezier
 * @author pissang (https://www.github.com/pissang)
 *         Kener (@Kener-林峰, kener.linfeng@gmail.com)
 *         errorrik (errorrik@gmail.com)
 */
import { min as v2Min, max as v2Max, scale as v2Scale, distance as v2Distance, add as v2Add, clone as v2Clone, sub as v2Sub } from '../../core/vector';
/**
 * 贝塞尔平滑曲线
 * @alias module:zrender/shape/util/smoothBezier
 * @param {Array} points 线段顶点数组
 * @param {number} smooth 平滑等级, 0-1
 * @param {boolean} isLoop
 * @param {Array} constraint 将计算出来的控制点约束在一个包围盒内
 *                           比如 [[0, 0], [100, 100]], 这个包围盒会与
 *                           整个折线的包围盒做一个并集用来约束控制点。
 * @param {Array} 计算出来的控制点数组
 */

export default function (points, smooth, isLoop, constraint) {
  var cps = [];
  var v = [];
  var v1 = [];
  var v2 = [];
  var prevPoint;
  var nextPoint;
  var min, max;

  if (constraint) {
    min = [Infinity, Infinity];
    max = [-Infinity, -Infinity];

    for (var i = 0, len = points.length; i < len; i++) {
      v2Min(min, min, points[i]);
      v2Max(max, max, points[i]);
    } // 与指定的包围盒做并集


    v2Min(min, min, constraint[0]);
    v2Max(max, max, constraint[1]);
  }

  for (var i = 0, len = points.length; i < len; i++) {
    var point = points[i];

    if (isLoop) {
      prevPoint = points[i ? i - 1 : len - 1];
      nextPoint = points[(i + 1) % len];
    } else {
      if (i === 0 || i === len - 1) {
        cps.push(v2Clone(points[i]));
        continue;
      } else {
        prevPoint = points[i - 1];
        nextPoint = points[i + 1];
      }
    }

    v2Sub(v, nextPoint, prevPoint); // use degree to scale the handle length

    v2Scale(v, v, smooth);
    var d0 = v2Distance(point, prevPoint);
    var d1 = v2Distance(point, nextPoint);
    var sum = d0 + d1;

    if (sum !== 0) {
      d0 /= sum;
      d1 /= sum;
    }

    v2Scale(v1, v, -d0);
    v2Scale(v2, v, d1);
    var cp0 = v2Add([], point, v1);
    var cp1 = v2Add([], point, v2);

    if (constraint) {
      v2Max(cp0, cp0, min);
      v2Min(cp0, cp0, max);
      v2Max(cp1, cp1, min);
      v2Min(cp1, cp1, max);
    }

    cps.push(cp0);
    cps.push(cp1);
  }

  if (isLoop) {
    cps.push(cps.shift());
  }

  return cps;
}