cross-gesture/lib/esm/utils.js

Gesture lib for the modern browsers

import { SwipeDirection } from './types';
export function vectorAbs(v) {
    return Math.sqrt(v.x * v.x + v.y * v.y);
}
export function vectorDot(f, t) {
    return f.x * t.x + f.y * t.y;
}
// 返回缩放的倍数
export function pinchTimes(from, to) {
    const fromLen = Math.sqrt(Math.pow(Math.abs(from[0].x - from[1].x), 2) + Math.pow(Math.abs(from[0].y - from[1].y), 2));
    const toLen = Math.sqrt(Math.pow(Math.abs(to[0].x - to[1].x), 2) + Math.pow(Math.abs(to[0].y - to[1].y), 2));
    return toLen / fromLen;
}
// 返回旋转的角度
// 顺时针为正数
export function getRotateDeg(from, to) {
    const fromVector = { x: from[1].x - from[0].x, y: from[1].y - from[0].y };
    const toVector = { x: to[1].x - to[0].x, y: to[1].y - to[0].y };
    // direction: https://blog.csdn.net/qq_42778110/article/details/81567954
    const direction = fromVector.x * toVector.y - fromVector.y * toVector.x;
    if (direction === 0) {
        return 0;
    }
    // a * b = |a|*|b|*cos(deg)
    // cos(deg) = (a * b) / (|a| * |b|)
    const cosDeg = vectorDot(fromVector, toVector) / (vectorAbs(fromVector) * vectorAbs(toVector));
    return (direction > 0 ? 1 : -1) * Math.acos(cosDeg);
}
// 返回滑动反向和速度
export function getDirectionAndSpeed(from, to, duration) {
    const distanceX = to.x - from.x;
    const distanceY = to.y - from.y;
    return {
        vDirection: distanceX > 0 ? SwipeDirection.right : SwipeDirection.left,
        vSpeed: distanceX / duration,
        hDirection: distanceY > 0 ? SwipeDirection.bottom : SwipeDirection.top,
        hSpeed: distanceY / duration,
    };
}
export function getCrossPoint(from, to) {
    // k = (y2 - y1) / (x2 - x1)
    // b = y1 - k * x1
    const k1 = (from[1].y - from[0].y) / (from[1].x - from[0].x);
    const b1 = from[0].y - k1 * from[0].x;
    const k2 = (to[1].y - to[0].y) / (to[1].x - to[0].x);
    const b2 = to[0].y - k2 * to[0].x;
    // x = (b1 - b2) / (k2 - k1)
    // y = k1x + b1
    const x = (b1 - b2) / (k2 - k1);
    return {
        x,
        y: k1 * x + b1,
    };
}
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