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三分钟HTML5画布(Canvas)动画教程-CSDN博客

时间:2021-07-01 10:21:17 帮助过:101人阅读

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。
这里写图片描述

这里写图片描述

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:

<script type="text/javascript" src="/js/kineticv5.0.1.min.js"></script>

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

<!DOCTYPE HTML><html>
  <head>
    <style>
      body {        margin: 0px;        padding: 0px;      }
      #container {        background-color: black;      }
    </style>
  </head>
  <body>
    <p id="container"></p>
    <script src="/js/lib/kinetic-v5.0.1.min.js"></script>
    <script defer="defer">
      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();
      });    </script>
  </body></html>

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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