85 lines
3.1 KiB
JavaScript
85 lines
3.1 KiB
JavaScript
"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
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var util_1 = require("./util");
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// 向量长度
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function vMag(v) {
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return Math.sqrt(v[0] * v[0] + v[1] * v[1]);
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}
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// u.v/|u||v|，计算夹角的余弦值
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function vRatio(u, v) {
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// 当存在一个向量的长度为 0 时，夹角也为 0，即夹角的余弦值为 1
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return vMag(u) * vMag(v) ? (u[0] * v[0] + u[1] * v[1]) / (vMag(u) * vMag(v)) : 1;
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}
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// 向量角度
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function vAngle(u, v) {
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return (u[0] * v[1] < u[1] * v[0] ? -1 : 1) * Math.acos(vRatio(u, v));
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}
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// A 0:rx 1:ry 2:x-axis-rotation 3:large-arc-flag 4:sweep-flag 5: x 6: y
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function getArcParams(startPoint, params) {
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var rx = params[1];
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var ry = params[2];
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var xRotation = util_1.mod(util_1.toRadian(params[3]), Math.PI * 2);
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var arcFlag = params[4];
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var sweepFlag = params[5];
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// 弧形起点坐标
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var x1 = startPoint[0];
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var y1 = startPoint[1];
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// 弧形终点坐标
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var x2 = params[6];
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var y2 = params[7];
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var xp = (Math.cos(xRotation) * (x1 - x2)) / 2.0 + (Math.sin(xRotation) * (y1 - y2)) / 2.0;
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var yp = (-1 * Math.sin(xRotation) * (x1 - x2)) / 2.0 + (Math.cos(xRotation) * (y1 - y2)) / 2.0;
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var lambda = (xp * xp) / (rx * rx) + (yp * yp) / (ry * ry);
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if (lambda > 1) {
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rx *= Math.sqrt(lambda);
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ry *= Math.sqrt(lambda);
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}
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var diff = rx * rx * (yp * yp) + ry * ry * (xp * xp);
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var f = diff ? Math.sqrt((rx * rx * (ry * ry) - diff) / diff) : 1;
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if (arcFlag === sweepFlag) {
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f *= -1;
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}
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if (isNaN(f)) {
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f = 0;
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}
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// 旋转前的起点坐标，且当长半轴和短半轴的长度为 0 时，坐标按 (0, 0) 处理
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var cxp = ry ? (f * rx * yp) / ry : 0;
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var cyp = rx ? (f * -ry * xp) / rx : 0;
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// 椭圆圆心坐标
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var cx = (x1 + x2) / 2.0 + Math.cos(xRotation) * cxp - Math.sin(xRotation) * cyp;
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var cy = (y1 + y2) / 2.0 + Math.sin(xRotation) * cxp + Math.cos(xRotation) * cyp;
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// 起始点的单位向量
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var u = [(xp - cxp) / rx, (yp - cyp) / ry];
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// 终止点的单位向量
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var v = [(-1 * xp - cxp) / rx, (-1 * yp - cyp) / ry];
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// 计算起始点和圆心的连线，与 x 轴正方向的夹角
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var theta = vAngle([1, 0], u);
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// 计算圆弧起始点和终止点与椭圆圆心连线的夹角
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var dTheta = vAngle(u, v);
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if (vRatio(u, v) <= -1) {
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dTheta = Math.PI;
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}
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if (vRatio(u, v) >= 1) {
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dTheta = 0;
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}
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if (sweepFlag === 0 && dTheta > 0) {
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dTheta = dTheta - 2 * Math.PI;
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}
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if (sweepFlag === 1 && dTheta < 0) {
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dTheta = dTheta + 2 * Math.PI;
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}
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return {
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cx: cx,
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cy: cy,
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// 弧形的起点和终点相同时，长轴和短轴的长度按 0 处理
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rx: util_1.isSamePoint(startPoint, [x2, y2]) ? 0 : rx,
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ry: util_1.isSamePoint(startPoint, [x2, y2]) ? 0 : ry,
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startAngle: theta,
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endAngle: theta + dTheta,
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xRotation: xRotation,
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arcFlag: arcFlag,
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sweepFlag: sweepFlag,
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};
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}
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exports.default = getArcParams;
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//# sourceMappingURL=arc-params.js.map
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