动画脚本Tween-优快云博客

本文深入探讨了Tween动画引擎的核心源码，包括线性、二次、三次、四次、五次、正弦、指数、圆弧、弹性、回弹等关键动画效果的数学公式实现。通过理解这些基础动画原理，开发者能够更灵活地运用Tween来实现丰富的视觉动画效果。

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贴上一个Tween的源码。

var Tween = {
	Linear: function(t,b,c,d){ return c*t/d + b; },
	Quad: {
		easeIn: function(t,b,c,d){
			return c*(t/=d)*t + b;
		},
		easeOut: function(t,b,c,d){
			return -c *(t/=d)*(t-2) + b;
		},
		easeInOut: function(t,b,c,d){
			if ((t/=d/2) < 1) return c/2*t*t + b;
			return -c/2 * ((--t)*(t-2) - 1) + b;
		}
	},
	Cubic: {
		easeIn: function(t,b,c,d){
			return c*(t/=d)*t*t + b;
		},
		easeOut: function(t,b,c,d){
			return c*((t=t/d-1)*t*t + 1) + b;
		},
		easeInOut: function(t,b,c,d){
			if ((t/=d/2) < 1) return c/2*t*t*t + b;
			return c/2*((t-=2)*t*t + 2) + b;
		}
	},
	Quart: {
		easeIn: function(t,b,c,d){
			return c*(t/=d)*t*t*t + b;
		},
		easeOut: function(t,b,c,d){
			return -c * ((t=t/d-1)*t*t*t - 1) + b;
		},
		easeInOut: function(t,b,c,d){
			if ((t/=d/2) < 1) return c/2*t*t*t*t + b;
			return -c/2 * ((t-=2)*t*t*t - 2) + b;
		}
	},
	Quint: {
		easeIn: function(t,b,c,d){
			return c*(t/=d)*t*t*t*t + b;
		},
		easeOut: function(t,b,c,d){
			return c*((t=t/d-1)*t*t*t*t + 1) + b;
		},
		easeInOut: function(t,b,c,d){
			if ((t/=d/2) < 1) return c/2*t*t*t*t*t + b;
			return c/2*((t-=2)*t*t*t*t + 2) + b;
		}
	},
	Sine: {
		easeIn: function(t,b,c,d){
			return -c * Math.cos(t/d * (Math.PI/2)) + c + b;
		},
		easeOut: function(t,b,c,d){
			return c * Math.sin(t/d * (Math.PI/2)) + b;
		},
		easeInOut: function(t,b,c,d){
			return -c/2 * (Math.cos(Math.PI*t/d) - 1) + b;
		}
	},
	Expo: {
		easeIn: function(t,b,c,d){
			return (t==0) ? b : c * Math.pow(2, 10 * (t/d - 1)) + b;
		},
		easeOut: function(t,b,c,d){
			return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
		},
		easeInOut: function(t,b,c,d){
			if (t==0) return b;
			if (t==d) return b+c;
			if ((t/=d/2) < 1) return c/2 * Math.pow(2, 10 * (t - 1)) + b;
			return c/2 * (-Math.pow(2, -10 * --t) + 2) + b;
		}
	},
	Circ: {
		easeIn: function(t,b,c,d){
			return -c * (Math.sqrt(1 - (t/=d)*t) - 1) + b;
		},
		easeOut: function(t,b,c,d){
			return c * Math.sqrt(1 - (t=t/d-1)*t) + b;
		},
		easeInOut: function(t,b,c,d){
			if ((t/=d/2) < 1) return -c/2 * (Math.sqrt(1 - t*t) - 1) + b;
			return c/2 * (Math.sqrt(1 - (t-=2)*t) + 1) + b;
		}
	},
	Elastic: {
		easeIn: function(t,b,c,d,a,p){
			if (t==0) return b;  if ((t/=d)==1) return b+c;  if (!p) p=d*.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;
		},
		easeOut: function(t,b,c,d,a,p){
			if (t==0) return b;  if ((t/=d)==1) return b+c;  if (!p) p=d*.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);
		},
		easeInOut: function(t,b,c,d,a,p){
			if (t==0) return b;  if ((t/=d/2)==2) return b+c;  if (!p) p=d*(.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 -.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 )*.5 + c + b;
		}
	},
	Back: {
		easeIn: function(t,b,c,d,s){
			if (s == undefined) s = 1.70158;
			return c*(t/=d)*t*((s+1)*t - s) + b;
		},
		easeOut: function(t,b,c,d,s){
			if (s == undefined) s = 1.70158;
			return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
		},
		easeInOut: function(t,b,c,d,s){
			if (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;
		}
	},
	Bounce: {
		easeIn: function(t,b,c,d){
			return c - Tween.Bounce.easeOut(d-t, 0, c, d) + b;
		},
		easeOut: 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 + .75) + b;
			} else if (t < (2.5/2.75)) {
				return c*(7.5625*(t-=(2.25/2.75))*t + .9375) + b;
			} else {
				return c*(7.5625*(t-=(2.625/2.75))*t + .984375) + b;
			}
		},
		easeInOut: function(t,b,c,d){
			if (t < d/2) return Tween.Bounce.easeIn(t*2, 0, c, d) * .5 + b;
			else return Tween.Bounce.easeOut(t*2-d, 0, c, d) * .5 + c*.5 + b;
		}
	}
};