怎么样基于HTML5+webkit实现树叶飘落动画？
实现如图所示的东西效果（落叶下落）：
html代码：
<!DOCTYPE html>
<html>
<head>
<title>HTML5树叶飘落动画</title>
<meta charset="utf-8">
<meta name="viewport" content="width=500px, initial-scale=0.64">
<link rel="stylesheet" href="leaves.css" type="text/css">
<script src="leaves.js" type="text/javascript"></script>
</head>
<body>
<div id="container">
<div id="leafContainer"></div>
<div id="message">
<em>这是基于webkit的落叶动画</em>
</div>
</div>
</body>
</html>
css代码：
body{
background-color: #4E4226;
}
#container {
position: relative;
height: 700px;
width: 500px;
margin: 10px auto;
overflow: hidden;
border: 4px solid #5C090A;
background: #4E4226 url('images/backgroundLeaves.jpg') no-repeat top left;
}
#leafContainer {
position: absolute;
width: 100%;
height: 100%;
}
#message{
position: absolute;
top: 160px;
width: 100%;
height: 300px;
background:transparent url('images/textBackground.png') repeat-x center;
color: #5C090A;
font-size: 220%;
font-family: 'Georgia';
text-align: center;
padding: 20px 10px;
-webkit-box-sizing: border-box;
-webkit-background-size: 100% 100%;
z-index: 1;
}
em {
font-weight: bold;
font-style: normal;
}
#leafContainer > div {
position: absolute;
width: 100px;
height: 100px;
-webkit-animation-iteration-count: infinite;
-webkit-animation-direction: normal;
-webkit-animation-timing-function: linear;
}
#leafContainer > div > img {
position: absolute;
width: 100px;
height: 100px;
-webkit-animation-iteration-count: infinite;
-webkit-animation-direction: alternate;
-webkit-animation-timing-function: ease-in-out;
-webkit-transform-origin: 50% -100%;
}
@-webkit-keyframes fade{
0% { opacity: 1; }
95% { opacity: 1; }
100% { opacity: 0; }
}
@-webkit-keyframes drop{
0% { -webkit-transform: translate(0px, -50px); }
100% { -webkit-transform: translate(0px, 650px); }
}
@-webkit-keyframes clockwiseSpin{
0% { -webkit-transform: rotate(-50deg); }
100% { -webkit-transform: rotate(50deg); }
}
@-webkit-keyframes counterclockwiseSpinAndFlip {
0% { -webkit-transform: scale(-1, 1) rotate(50deg); }
100% { -webkit-transform: scale(-1, 1) rotate(-50deg); }
}
js代码：
const NUMBER_OF_LEAVES = 30;
function init(){
var container = document.getElementById('leafContainer');
for (var i = 0; i < NUMBER_OF_LEAVES; i++) {
container.appendChild(createALeaf());
}
}
function randomInteger(low, high){
return low + Math.floor(Math.random() * (high - low));
}
function randomFloat(low, high){
return low + Math.random() * (high - low);
}
function pixelValue(value){
return value + 'px';
}
function durationValue(value){
return value + 's';
}
function createALeaf(){
var leafDiv = document.createElement('div');
leafDiv.style.top = "-100px";
leafDiv.style.left = pixelValue(randomInteger(0, 500));
leafDiv.style.webkitAnimationName = 'fade, drop';
var fadeAndDropDuration = durationValue(randomFloat(5, 11));
leafDiv.style.webkitAnimationDuration = fadeAndDropDuration + ', ' + fadeAndDropDuration;
var leafDelay = durationValue(randomFloat(0, 5));
leafDiv.style.webkitAnimationDelay = leafDelay + ', ' + leafDelay;
var image = document.createElement('img');
image.src = 'images/realLeaf' + randomInteger(1, 5) + '.png';
var spinAnimationName = (Math.random() < 0.5) ? 'clockwiseSpin' : 'counterclockwiseSpinAndFlip';
image.style.webkitAnimationName = spinAnimationName;
var spinDuration = durationValue(randomFloat(4, 8));
image.style.webkitAnimationDuration = spinDuration;
leafDiv.appendChild(image);
return leafDiv;
}
window.addEventListener('load', init, false);
PS：下面看下html5 canvas处理连续帧图片,下面的代码基于IE8以上
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no"/>
<title>Canvas Demo</title>
<script>
var canvas = null;//初始化参数
var img = null;
var ctx = null;
var imageReady = false;
window.onload = function() {
var canvas = document.getElementById("animation_canvas");
canvas.width = canvas.parentNode.clientWidth;
canvas.height = canvas.parentNode.clientHeight;
if (!canvas.getContext) {
console.log("Canvas not supported. Please install a HTML5 compatible browser.");
return;
}
// get 2D context of canvas and draw rectangel
ctx = canvas.getContext("2d");
ctx.fillStyle="black";
ctx.fillRect(0, 0, canvas.width, canvas.height);
console.log(canvas.height);
img = document.createElement('img');
img.src = "images/ab0.png";
img.onload = loaded();
}
//保证只有图像加载后才开始循环动画
function loaded() {
imageReady = true;
setTimeout( update, 1000/3);//添加3帧每秒间隔计时器
}
function redraw() {
ctx.fillStyle="black";
ctx.fillRect(0, 0, 460, 460);
ctx.drawImage(img, 0, 0, 232, 180);
}
//为了让图片以规定的速度动画，我们必须追踪已经经过的时间，然后根据分配给每帧的时间播放郑基本步骤是：
//1、按每秒几帧设置动画速度(msPerFrame)。
//2、当你循环游戏时，计算一下自最后一帧以后已经经过了多少时间（delta）。
//3、如果已经经过的时间足够把动画帧播完，那么播放这一帧并设置累积delta为0。
//4、如果已经经过的时间不够，那么记住（累积）delta时间（acDelta）。
var frame = 0;
var lastUpdateTime = 0;
var acDelta = 0;
var msPerFrame = 200;
function update() {
requestAnimFrame(update);
var delta = Date.now() - lastUpdateTime;
//console.log(Date.now(),lastUpdateTime);
if (acDelta > msPerFrame){
acDelta = 0;
redraw();
img.src='images/ab'+frame+'.png';
frame++;
if(frame >= 3) frame = 0; //当绘制后且帧推进完，计时器就会重置。
}else{
acDelta += delta;
}
lastUpdateTime = Date.now();
}
//requestAnimFrame的作用基本上就是setTimeout，但浏览器知道你正在渲染帧，所以它可以优化绘制循环，以及如何与剩下的页面回流。
//在某些情况下，setTimeout比requestAnimFrame更好用，特别是对于手机。
//以下是在不同的浏览器上调用requestAnimFrame的情况也不同，标准的检测方法如下：
window.requestAnimFrame = (function(){
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function( callback ){
window.setTimeout(callback, 1000 / 3); //如果requestAnimFrame支持不可用，还是可以用回内置的setTimeout。
};
})();
</script>
</head>
<body style="position:absolute;margin:0;padding:0;width:100%;height:100%;">
<canvas id="animation_canvas"></canvas>
</body>
</html>
总结
以上所述是小编给大家介绍的基于HTML5+Webkit实现树叶飘落动画，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对路饭网站的支持！
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