此文下面的教程中将使用的是另外一个叫做kinetic的Web动画工具包。

它们都是开源的。

把鼠标放到上面的小丑脸上，然后移开，就会有如下效果。

第一步，画五官

这个小丑没有耳朵和眉毛，所以只剩下三官，但它的两个眼睛我们要分别绘制，所以一共是四个部分。下面先看看代码。

绘制左眼的代码var leftEye = new Kinetic.Line({

x: 150,

points: [0, 200, 50, 190, 100, 200, 50, 210],

tension: 0.5,

closed: true,

stroke: 'white',

strokeWidth: 10

});

绘制右眼的代码var rightEye = new Kinetic.Line({

x: sw - 250,

points: [0, 200, 50, 190, 100, 200, 50, 210],

tension: 0.5,

closed: true,

stroke: 'white',

strokeWidth: 10

});

绘制鼻子的代码var nose = new Kinetic.Line({

points: [240, 280, sw/2, 300, sw-240,280],

tension: 0.5,

closed: true,

stroke: 'white',

strokeWidth: 10

});

绘制嘴巴的代码var mouth = new Kinetic.Line({

points: [150, 340, sw/2, 380, sw - 150, 340, sw/2, sh],

tension: 0.5,

closed: true,

stroke: 'red',

strokeWidth: 10

});

简单讲解一下上面的代码。Kinetic就是我们使用的js工具包。在页面的头部，我们需要这样引用它：

其它几个分别是几个关键点，线条弹性，颜色，宽度等。这些都很容易理解。

第二步，让图动起来

这个动画之所以能吸引人，是因为它能响应你的鼠标动作，和用户有互动，这是一个成功的动画最关键的地方。如果你仔细观察，这个小丑五官的变化只是形状的变化，眼睛变大，嘴巴变大，鼻子变大，但特别的是这个变化不是瞬间变化，而是有过渡性的，这里面有一些算法，这就是最让人发愁的地方。幸运的是，这算法技术都非常的成熟，不需要我们来思考，在这些动画引擎库里都把这些技术封装成了非常简单方便的接口。下面我们来看看如何让动起来。

左眼的动画var leftEyeTween = new Kinetic.Tween({

node: leftEye,

duration: 1,

easing: Kinetic.Easings.ElasticEaseOut, y: -100,

points: [0, 200, 50, 150, 100, 200, 50, 200]

});

右眼的动画var rightEyeTween = new Kinetic.Tween({

node: rightEye,

duration: 1,

easing: Kinetic.Easings.ElasticEaseOut, y: -100,

points: [0, 200, 50, 150, 100, 200, 50, 200]

});

鼻子的动画var noseTween = new Kinetic.Tween({

node: nose,

duration: 1,

easing: Kinetic.Easings.ElasticEaseOut, y: -100,

points: [220, 280, sw/2, 200, sw-220,280]

});

嘴巴的动画var mouthTween = new Kinetic.Tween({

node: mouth,

duration: 1,

easing: Kinetic.Easings.ElasticEaseOut,

points: [100, 250, sw/2, 250, sw - 100, 250, sw/2, sh-20]

});

这些代码非常的简单，而且变量名能自释其意。稍微有点经验的程序员想看懂这些代码应该不难。基本每段代码都是让你提供一些点，指定动画动作的衰退模式和持续时间。

完整的动画代码

body { margin: 0px; padding: 0px; }

#container { background-color: black; }

var sw = 578; var sh = 400; var stage = new Kinetic.Stage({

container: 'container',

width: 578,

height: 400

}); var layer = new Kinetic.Layer({

y: -30

}); var leftEye = new Kinetic.Line({

x: 150,

points: [0, 200, 50, 190, 100, 200, 50, 210],

tension: 0.5,

closed: true,

stroke: 'white',

strokeWidth: 10

}); var rightEye = new Kinetic.Line({

x: sw - 250,

points: [0, 200, 50, 190, 100, 200, 50, 210],

tension: 0.5,

closed: true,

stroke: 'white',

strokeWidth: 10

}); var nose = new Kinetic.Line({

points: [240, 280, sw/2, 300, sw-240,280],

tension: 0.5,

closed: true,

stroke: 'white',

strokeWidth: 10

}); var mouth = new Kinetic.Line({

points: [150, 340, sw/2, 380, sw - 150, 340, sw/2, sh],

tension: 0.5,

closed: true,

stroke: 'red',

strokeWidth: 10

});

layer.add(leftEye)

.add(rightEye)

.add(nose)

.add(mouth);

stage.add(layer); // tweens

var leftEyeTween = new Kinetic.Tween({

node: leftEye,

duration: 1,

easing: Kinetic.Easings.ElasticEaseOut,

y: -100,

points: [0, 200, 50, 150, 100, 200, 50, 200]

});

var rightEyeTween = new Kinetic.Tween({

node: rightEye,

duration: 1,

easing: Kinetic.Easings.ElasticEaseOut,

y: -100,

points: [0, 200, 50, 150, 100, 200, 50, 200]

}); var noseTween = new Kinetic.Tween({

node: nose,

duration: 1,

easing: Kinetic.Easings.ElasticEaseOut,

y: -100,

points: [220, 280, sw/2, 200, sw-220,280]

});

var mouthTween = new Kinetic.Tween({

node: mouth,

duration: 1,

easing: Kinetic.Easings.ElasticEaseOut,

points: [100, 250, sw/2, 250, sw - 100, 250, sw/2, sh-20]

});

stage.getContainer().addEventListener('mouseover', function() {

leftEyeTween.play();

rightEyeTween.play();

noseTween.play();

mouthTween.play();

});

stage.getContainer().addEventListener('mouseout', function() {

leftEyeTween.reverse();

rightEyeTween.reverse();

noseTween.reverse();

mouthTween.reverse();

});

我相信你已经在3三分钟内看完并看懂了这个动画的制作过程和原理。当然，这个动画很简单，我们这里只是粗浅的讲解一些HTML5画布(Canvas)动画技术的皮毛。如果想真正的成为Web动画告诉，那你还需要做很多的努力。但如果你只是业余爱好，我相信这已经足够让你骄傲了。

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