<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>canvas</title>
<script type="text/javascript" src="../js/jQuery.js"></script>
<style type="text/css">
#canvas{
width: 7rem;
margin: .25rem 0 0 1.5rem;
border: 1px solid black;
display: block;
}
</style>
</head>
<body>
<canvas id="canvas" width="1000" height="600"></canvas>
<button>source-over</button>
<button>source-atop</button>
<button>source-in</button>
<button>source-out</button>
<button>destination-over</button>
<button>destination-atop</button>
<button>destination-in</button>
<button>destination-out</button>
<button>lighter</button>
<button>copy</button>
<button>xor</button>
</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');
/**
* globalCompositeOperation: 图形的折叠方式
*/
$('button').click(function(){
cxt.clearRect(0, 0, canvas.width, canvas.height);
cxt.globalCompositeOperation = $(this).html();
cxt.fillStyle = 'red';
cxt.fillRect(100, 100, 400, 200);
cxt.fillStyle = 'blue';
cxt.fillRect(300, 200, 400, 200);
});
</script>
<!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{
width: 7rem;
margin: .25rem 0 0 1.5rem;
border: 1px solid black;
}
</style>
</head>
<body>
<canvas id="canvas" width="1000" height="600"></canvas>
</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');
/**
* globalAlpha: 透明度
*/
for(var i = 0; i < 100; i++){
var R = Math.floor(Math.random()*225);
var G = Math.floor(Math.random()*225);
var B = Math.floor(Math.random()*225);
var x = R + "," + G + "," + B;
cxt.fillStyle = "rgb("+x+")";
cxt.globalAlpha = 0.7;
cxt.beginPath();
cxt.arc(Math.random()*canvas.width, Math.random()*canvas.height, Math.random()*70, 0, Math.PI*2);
cxt.fill();
}
</script>
