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CANVAS 水波动态背景

2016-04-11 17:39 162 查看

参考：https://github.com/cyclegtx/wave_background

做的水波背景，以后可能会用到哈！

效果如下：

代码如下：

<!DOCTYPE html>
<html>
<head>
<title>水波背景</title>
<meta charset="utf-8" />
<style>
html, body {width:100%; height:100%; padding:0; margin:0;}
</style>
</head>
<body>
<canvas id="canvas" style="position:absolute;top:0px;left:0px;z-index:1;"></canvas>
<script type="text/javascript">
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
canvas.width = canvas.parentNode.offsetWidth;
canvas.height = canvas.parentNode.offsetHeight;
//如果浏览器支持requestAnimFrame则使用requestAnimFrame否则使用setTimeout
window.requestAnimFrame = (function(){
return  window.requestAnimationFrame       ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame    ||
function( callback ){
window.setTimeout(callback, 1000 / 60);
};
})();
// 波浪大小
var boHeight = canvas.height / 10;
var posHeight = canvas.height / 1.2;
//初始角度为0
var step = 0;
//定义三条不同波浪的颜色
var lines = ["rgba(0,222,255, 0.2)",
"rgba(157,192,249, 0.2)",
"rgba(0,168,255, 0.2)"];
function loop(){
ctx.clearRect(0,0,canvas.width,canvas.height);
step++;
//画3个不同颜色的矩形
for(var j = lines.length - 1; j >= 0; j--) {
ctx.fillStyle = lines[j];
//每个矩形的角度都不同，每个之间相差45度
var angle = (step+j*50)*Math.PI/180;
var deltaHeight   = Math.sin(angle) * boHeight;
var deltaHeightRight   = Math.cos(angle) * boHeight;
ctx.beginPath();
ctx.moveTo(0, posHeight+deltaHeight);
ctx.bezierCurveTo(canvas.width/2, posHeight+deltaHeight-boHeight, canvas.width / 2, posHeight+deltaHeightRight-boHeight, canvas.width, posHeight+deltaHeightRight);
ctx.lineTo(canvas.width, canvas.height);
ctx.lineTo(0, canvas.height);
ctx.lineTo(0, posHeight+deltaHeight);
ctx.closePath();
ctx.fill();
}
requestAnimFrame(loop);
}
loop();
</script>
</body>
</html>

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