112 lines
3.0 KiB
TypeScript
112 lines
3.0 KiB
TypeScript
import line from './line';
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import { distance } from './util';
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import { Point, PointTuple, Segment } from './types';
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function analyzePoints(points: PointTuple[]) {
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// 计算每段的长度和总的长度
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let totalLength = 0;
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const segments: Segment[] = [];
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for (let i = 0; i < points.length - 1; i++) {
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const from = points[i];
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const to = points[i + 1];
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const length = distance(from[0], from[1], to[0], to[1]);
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const seg = {
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from,
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to,
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length,
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};
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segments.push(seg);
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totalLength += length;
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}
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return { segments, totalLength };
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}
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export function lengthOfSegment(points: PointTuple[]) {
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if (points.length < 2) {
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return 0;
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}
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let totalLength = 0;
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for (let i = 0; i < points.length - 1; i++) {
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const from = points[i];
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const to = points[i + 1];
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totalLength += distance(from[0], from[1], to[0], to[1]);
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}
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return totalLength;
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}
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/**
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* 按照比例在数据片段中获取点
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* @param {array} points 点的集合
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* @param {number} t 百分比 0-1
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* @return {object} 点的坐标
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*/
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export function pointAtSegments(points: PointTuple[], t: number): Point {
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// 边界判断
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if (t > 1 || t < 0 || points.length < 2) {
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return null;
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}
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const { segments, totalLength } = analyzePoints(points);
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// 多个点有可能重合
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if (totalLength === 0) {
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return {
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x: points[0][0],
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y: points[0][1],
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};
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}
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// 计算比例
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let startRatio = 0;
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let point = null;
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for (let i = 0; i < segments.length; i++) {
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const seg = segments[i];
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const { from, to } = seg;
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const currentRatio = seg.length / totalLength;
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if (t >= startRatio && t <= startRatio + currentRatio) {
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const localRatio = (t - startRatio) / currentRatio;
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point = line.pointAt(from[0], from[1], to[0], to[1], localRatio);
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break;
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}
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startRatio += currentRatio;
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}
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return point;
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}
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/**
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* 按照比例在数据片段中获取切线的角度
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* @param {array} points 点的集合
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* @param {number} t 百分比 0-1
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*/
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export function angleAtSegments(points: PointTuple[], t: number) {
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// 边界判断
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if (t > 1 || t < 0 || points.length < 2) {
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return 0;
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}
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const { segments, totalLength } = analyzePoints(points);
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// 计算比例
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let startRatio = 0;
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let angle = 0;
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for (let i = 0; i < segments.length; i++) {
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const seg = segments[i];
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const { from, to } = seg;
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const currentRatio = seg.length / totalLength;
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if (t >= startRatio && t <= startRatio + currentRatio) {
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angle = Math.atan2(to[1] - from[1], to[0] - from[0]);
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break;
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}
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startRatio += currentRatio;
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}
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return angle;
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}
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export function distanceAtSegment(points: PointTuple[], x: number, y: number) {
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let minDistance = Infinity;
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for (let i = 0; i < points.length - 1; i++) {
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const point = points[i];
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const nextPoint = points[i + 1];
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const distance = line.pointDistance(point[0], point[1], nextPoint[0], nextPoint[1], x, y);
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if (distance < minDistance) {
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minDistance = distance;
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}
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}
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return minDistance;
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}
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