Merge branch 'master' of https://git.code.tencent.com/jl-framework/graphic-pixi

src/jlgraphic/utils/GraphicUtils.ts

@@ -2,6 +2,7 @@ import {
   Container,
   DisplayObject,
   IPointData,
+  Matrix,
   Point,
   Rectangle,
 } from 'pixi.js';
@@ -693,3 +694,44 @@ export function splitLineEvenly(
       ];
     });
 }
+
+export function getParallelOfPolyline(
+  points: IPointData[],
+  offset: number,
+  side: 'L' | 'R'
+): IPointData[] {
+  const { PI, cos, acos } = Math;
+  const angleBase = side === 'L' ? -PI / 2 : PI / 2;
+  return points.map((p, i) => {
+    let baseUnitVec: Vector2; //上一段的基准单位向量
+    let angle: number; //偏转角度
+    let len: number; //结合偏转角度的实际偏移量
+    if (!points[i - 1] || !points[i + 1]) {
+      angle = angleBase;
+      len = offset;
+      baseUnitVec = points[i - 1]
+        ? new Vector2([
+            p.x - points[i - 1].x,
+            p.y - points[i - 1].y,
+          ]).normalize()
+        : new Vector2([
+            points[i + 1].x - p.x,
+            points[i + 1].y - p.y,
+          ]).normalize();
+    } else {
+      const vp = new Vector2([p.x - points[i - 1].x, p.y - points[i - 1].y]);
+      const vn = new Vector2([points[i + 1].x - p.x, points[i + 1].y - p.y]);
+      const cosTheta = Vector2.dot(vn, vp) / (vp.length() * vn.length());
+      const direction = vp.x * vn.y - vp.y * vn.x > 0; //det(vp|vn)>0?
+      const theta = direction ? acos(cosTheta) : -acos(cosTheta);
+      angle = angleBase + theta / 2;
+      len = offset / cos(theta / 2);
+      baseUnitVec = Vector2.from(vp).normalize();
+    }
+    return new Matrix()
+      .scale(len, len)
+      .rotate(angle)
+      .translate(p.x, p.y)
+      .apply(baseUnitVec);
+  });
+}