canvas绘制矩形
1.效果图
2.实现代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="/static/css/common.css">
<title>Document</title>
</head>
<body>
<canvas id="example" width="512" height="512">
游览器不支持
</canvas>
</body>
<script>
var canvas = document.getElementById('example');
if(canvas==null){
alert("获取失败")
}
var ctx = canvas.getContext('2d');
console.log(ctx);
var w = ctx.canvas.width;
var h = ctx.canvas.height;
ctx.fillstyle = 'rgba(255,0,255,0.5)';
ctx.fillRect(w/2-200,h/2-100,400,200);
</script>
</html>
common.css
body {
padding: 0;
margin: 0;
overflow: hidden;
}
canvas {
display: block;
border: 1px dashed rgba(0, 100, 100, 1.0);
margin: 50px auto;
}