41 lines
1.3 KiB
TypeScript
41 lines
1.3 KiB
TypeScript
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export type Point = {
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x: number;
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y: number;
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};
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export class DiamondCheck {
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// 计算两个向量的叉积的绝对值
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static crossProduct(a: Point, b: Point, p: Point): number {
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return (b.x - a.x) * (p.y - a.y) - (b.y - a.y) * (p.x - a.x);
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}
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// 判断点p是否在由顶点a, b, c, d定义的多边形内部
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static isPointInDiamond(
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point: Point,
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diamondCoords: [Point,Point,Point,Point]
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): boolean {
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const [a,b,c,d] = diamondCoords;
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// 计算多边形的边
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const ab = { x: b.x - a.x, y: b.y - a.y };
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const bc = { x: c.x - b.x, y: c.y - b.y };
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const cd = { x: d.x - c.x, y: d.y - c.y };
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const da = { x: a.x - d.x, y: a.y - d.y };
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// 计算点p与多边形每条边的叉积
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const abP = DiamondCheck.crossProduct(a, b, point);
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const bcP = DiamondCheck.crossProduct(b, c, point);
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const cdP = DiamondCheck.crossProduct(c, d, point);
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const daP = DiamondCheck.crossProduct(d, a, point);
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// 如果所有叉积的符号一致（即绝对值相同），点p在多边形内部
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const allSameSign = (a: number, b: number, c: number, d: number): boolean =>
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Math.sign(a) === Math.sign(b) &&
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Math.sign(b) === Math.sign(c) &&
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Math.sign(c) === Math.sign(d);
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return allSameSign(abP, bcP, cdP, daP);
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}
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}
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