<!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');
/**
* 画圆 arc( 圆心的横坐标, 圆心的纵坐标, 半径的长度, 绘制的起始角度, 绘制的终结角度, 是否逆时针 )
* 圆弧 arcTo(第一个控制点的横坐标, 第一个个控制点的纵坐标, 第二个人控制点的横坐标, 第二个控制点的纵坐标, 圆弧的半径)
*/
/*
cxt.arc(500, 300, 100, 0, 2*Math.PI, false);
cxt.fill();
*/
cxt.save();
cxt.lineWidth = 3;
cxt.strokeStyle = 'red';
cxt.moveTo(100, 100);
cxt.arcTo(700, 100, 700, 500, 300);
cxt.stroke();
cxt.restore();
/**
* 辅助线
*/
cxt.strokeStyle = 'green';
cxt.moveTo(100, 100);
cxt.lineTo(700, 100);
cxt.lineTo(700, 500);
cxt.stroke();
</script>