bd028579
 易尊强
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/**
* 贝塞尔平滑曲线
*/
import {
min as v2Min,
max as v2Max,
scale as v2Scale,
distance as v2Distance,
add as v2Add,
clone as v2Clone,
sub as v2Sub,
VectorArray
} from '../../core/vector';
/**
* 贝塞尔平滑曲线
* @param points 线段顶点数组
* @param smooth 平滑等级, 0-1
* @param isLoop
* @param 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 计算出来的控制点数组
*/
export default function smoothBezier(
points: VectorArray[],
smooth?: number,
isLoop?: boolean,
constraint?: VectorArray[]
) {
const cps = [];
const v: VectorArray = [];
const v1: VectorArray = [];
const v2: VectorArray = [];
let prevPoint;
let nextPoint;
let min;
let max;
if (constraint) {
min = [Infinity, Infinity];
max = [-Infinity, -Infinity];
for (let 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 (let i = 0, len = points.length; i < len; i++) {
const 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);
let d0 = v2Distance(point, prevPoint);
let d1 = v2Distance(point, nextPoint);
const sum = d0 + d1;
if (sum !== 0) {
d0 /= sum;
d1 /= sum;
}
v2Scale(v1, v, -d0);
v2Scale(v2, v, d1);
const cp0 = v2Add([], point, v1);
const 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;
}
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