• Tween公式 以及四个参数


      Tween的主页在这里:http://createjs.com/tweenjs , 这里边还有挺多开源项目的;

      Tween公式 4个参数

    t:current time(当前时间) 

    b:beginning value(初始值)

    c: change in value(变化量)

    d:duration(持续时间) return (目标点)

    var Tween = {
        linear: function (t, b, c, d){  //匀速
            return c*t/d + b;
        },
        easeIn: function(t, b, c, d){  //加速曲线
            return c*(t/=d)*t + b;
        },
        easeOut: function(t, b, c, d){  //减速曲线
            return -c *(t/=d)*(t-2) + b;
        },
        easeBoth: function(t, b, c, d){  //加速减速曲线
            if ((t/=d/2) < 1) {
                return c/2*t*t + b;
            }
            return -c/2 * ((--t)*(t-2) - 1) + b;
        },
        easeInStrong: function(t, b, c, d){  //加加速曲线
            return c*(t/=d)*t*t*t + b;
        },
        easeOutStrong: function(t, b, c, d){  //减减速曲线
            return -c * ((t=t/d-1)*t*t*t - 1) + b;
        },
        easeBothStrong: function(t, b, c, d){  //加加速减减速曲线
            if ((t/=d/2) < 1) {
                return c/2*t*t*t*t + b;
            }
            return -c/2 * ((t-=2)*t*t*t - 2) + b;
        },
        elasticIn: function(t, b, c, d, a, p){  //正弦衰减曲线(弹动渐入)
            if (t === 0) { 
                return b; 
            }
            if ( (t /= d) == 1 ) {
                return b+c; 
            }
            if (!p) {
                p=d*0.3; 
            }
            if (!a || a < Math.abs(c)) {
                a = c; 
                var s = p/4;
            } else {
                var s = p/(2*Math.PI) * Math.asin (c/a);
            }
            return -(a*Math.pow(2,10*(t-=1)) * Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
        },
        elasticOut: function(t, b, c, d, a, p){    //正弦增强曲线(弹动渐出)
            if (t === 0) {
                return b;
            }
            if ( (t /= d) == 1 ) {
                return b+c;
            }
            if (!p) {
                p=d*0.3;
            }
            if (!a || a < Math.abs(c)) {
                a = c;
                var s = p / 4;
            } else {
                var s = p/(2*Math.PI) * Math.asin (c/a);
            }
            return a*Math.pow(2,-10*t) * Math.sin( (t*d-s)*(2*Math.PI)/p ) + c + b;
        },    
        elasticBoth: function(t, b, c, d, a, p){
            if (t === 0) {
                return b;
            }
            if ( (t /= d/2) == 2 ) {
                return b+c;
            }
            if (!p) {
                p = d*(0.3*1.5);
            }
            if ( !a || a < Math.abs(c) ) {
                a = c; 
                var s = p/4;
            }
            else {
                var s = p/(2*Math.PI) * Math.asin (c/a);
            }
            if (t < 1) {
                return - 0.5*(a*Math.pow(2,10*(t-=1)) * 
                        Math.sin( (t*d-s)*(2*Math.PI)/p )) + b;
            }
            return a*Math.pow(2,-10*(t-=1)) * 
                    Math.sin( (t*d-s)*(2*Math.PI)/p )*0.5 + c + b;
        },
        backIn: function(t, b, c, d, s){     //回退加速(回退渐入)
            if (typeof s == 'undefined') {
               s = 1.70158;
            }
            return c*(t/=d)*t*((s+1)*t - s) + b;
        },
        backOut: function(t, b, c, d, s){
            if (typeof s == 'undefined') {
                s = 3.70158;  //回缩的距离
            }
            return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
        }, 
        backBoth: function(t, b, c, d, s){
            if (typeof s == 'undefined') {
                s = 1.70158; 
            }
            if ((t /= d/2 ) < 1) {
                return c/2*(t*t*(((s*=(1.525))+1)*t - s)) + b;
            }
            return c/2*((t-=2)*t*(((s*=(1.525))+1)*t + s) + 2) + b;
        },
        bounceIn: function(t, b, c, d){    //弹球减振(弹球渐出)
            return c - Tween['bounceOut'](d-t, 0, c, d) + b;
        },       
        bounceOut: function(t, b, c, d){
            if ((t/=d) < (1/2.75)) {
                return c*(7.5625*t*t) + b;
            } else if (t < (2/2.75)) {
                return c*(7.5625*(t-=(1.5/2.75))*t + 0.75) + b;
            } else if (t < (2.5/2.75)) {
                return c*(7.5625*(t-=(2.25/2.75))*t + 0.9375) + b;
            }
            return c*(7.5625*(t-=(2.625/2.75))*t + 0.984375) + b;
        },      
        bounceBoth: function(t, b, c, d){
            if (t < d/2) {
                return Tween['bounceIn'](t*2, 0, c, d) * 0.5 + b;
            }
            return Tween['bounceOut'](t*2-d, 0, c, d) * 0.5 + c*0.5 + b;
        }
    }

      在平常使用jQuey或者写运动效果都是使用根据目标终点运动的库, 如果要用到和时间有关的运动咋办,  那么就可以根据miaov的完美运动框架改一改, 把计算速度的过程,使用Tween的方法替代:

    <html>
    <head>
        <title></title>
    //记得引用这个JS <script src="tween.js"></script> <style type="text/css"> div{ 100px; height:100px; position:absolute; left:10px; top:100px; background:#f00; } div:hover{ 400px; } </style> </head> <body> <div id="div"> </div> <script> window.onload = function() { move(eDiv, "left", "300",1000, "linear") } var getStyle = function(el, prop) { return window.getComputedStyle(el)[prop]; } var move = function(el, prop, dest, duration , fx) { var start = new Date().getTime(); var startValue = parseFloat(getStyle(el, prop)); var changeValue = dest - startValue; var timer = setInterval(function() { //1:当前时间 new Date - start; //2:初始值; //3:变化量; //4:持续时间 duration; var value = Tween[fx](new Date-start, startValue, changeValue, duration); if(prop === "opacity") { el.style[prop] = value; }else{ el.style[prop] = value + "px"; } if(new Date()>=duration+start) { clearInterval(timer); if(prop === "opacity") { el.style[prop] = dest; }else{ el.style[prop] = dest + "px"; } } },30); }; var eDiv = document.getElementById("div"); </script> </body> </html>

      

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  • 原文地址:https://www.cnblogs.com/diligenceday/p/5934190.html
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