<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>canvas</title>
<script type="text/javascript" src="../js/jQuery.js"></script>
<style type="text/css">
*{
margin: 0;
padding: 0;
outline: none;
border: none;
}
#canvas{
margin: auto auto;
width: 7rem;
margin: .25rem 0 0 1.5rem;
border: 1px solid black;
}
</style>
</head>
<body>
<canvas id="canvas" width="800" height="800"></canvas>
<img id="img" src="" />
</body>
</html>
<script type="text/javascript">
/**
* rem 布局初始化
*/
$('html').css('font-size', $(window).width()/10);
/**
* 获取 canvas 画布
* 获取 canvas 绘图上下文环境
*/
var canvas = $('#canvas')[0];
var cxt = canvas.getContext('2d');
/**
* 创建图形数据对象
* createImageData(宽, 高)
*/
var imgData = cxt.createImageData(canvas.width, canvas.height);
var pxData = imgData.data;
for(var i = 0; i < canvas.width; i++){
for(var j = 0; j < canvas.height; j++){
var p = canvas.width*i+j;
pxData[4*p+0] = parseInt(Math.pow(Math.cos(Math.atan2(j-400,i-400)/2),2)*255);
pxData[4*p+1] = parseInt(Math.pow(Math.cos(Math.atan2(j-400,i-400)/2-2*Math.acos(-1)/3),2)*255);
pxData[4*p+2] = parseInt(Math.pow(Math.cos(Math.atan2(j-400,i-400)/2+2*Math.acos(-1)/3),2)*255);
pxData[4*p+3] = 255;
}
}
cxt.putImageData(imgData, 0,0,0,0,canvas.width,canvas.height);
</script>
