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/**
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* 生成随机字符串
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* @param len 生成个数
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*/
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export const randomString = (len?: number) => {
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len = len || 10;
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const str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
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const maxPos = str.length;
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let random_str = '';
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for (let i = 0; i < len; i++) {
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random_str += str.charAt(Math.floor(Math.random() * maxPos));
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}
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return random_str;
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};
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// 通过泛型定义通用类型保护函数
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export const isOfType = <T>(target: unknown, prop: keyof T): target is T => {
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return (target as T)[prop] !== undefined;
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};
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/**
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* 获取坐标偏移量
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* @param length 真实宽/高
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* @param scale 缩放倍数
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* @returns 坐标偏移量
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*/
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export const getCoordinateOffset = (length: number, scale: number) => {
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return (length / 2) * (scale - 1);
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};
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// 角度转弧度
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// Math.PI = 180 度
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export const angleToRadian = (angle: number) => {
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return (angle * Math.PI) / 180;
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};
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/**
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* 计算根据圆心旋转后的点的坐标
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* @param {Object} point 旋转前的点坐标
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* @param {Object} center 旋转中心
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* @param {Number} rotate 旋转的角度
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* @return {Object} 旋转后的坐标
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* https://www.zhihu.com/question/67425734/answer/252724399 旋转矩阵公式
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*/
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export const calculateRotatedPointCoordinate = (
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point: { x: number; y: number },
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center: { x: number; y: number },
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rotate: number
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) => {
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/**
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* 旋转公式：
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* 点a(x, y)
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* 旋转中心c(x, y)
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* 旋转后点n(x, y)
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* 旋转角度θ tan ??
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* nx = cosθ * (ax - cx) - sinθ * (ay - cy) + cx
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* ny = sinθ * (ax - cx) + cosθ * (ay - cy) + cy
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*/
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return {
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x:
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(point.x - center.x) * Math.cos(angleToRadian(rotate)) -
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(point.y - center.y) * Math.sin(angleToRadian(rotate)) +
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center.x,
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y:
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(point.x - center.x) * Math.sin(angleToRadian(rotate)) +
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(point.y - center.y) * Math.cos(angleToRadian(rotate)) +
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center.y
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};
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};
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// 求两点之间的中点坐标
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export const getCenterPoint = (p1: { x: number; y: number }, p2: { x: number; y: number }) => {
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return {
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x: p1.x + (p2.x - p1.x) / 2,
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y: p1.y + (p2.y - p1.y) / 2
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};
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};
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