绘制矩形
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>绘制矩形</title>
</head>
<body>
<canvas id="drawing" height="500" width="500">A drawing of something.</canvas>
<script type="text/javascript">
var drawing = document.getElementById("drawing")
if(drawing.getContext)
{
var context = drawing.getContext("2d")
context.strokeStyle.lineCap = "square"
//绘制红色矩形
context.fillStyle = "#ff0000";
context.strokeStyle = "black"
context.fillRect(10,10,60,60);
context.strokeRect(10,10,60,60);
//绘制半透明的蓝色矩形
context.strokeStyle = "red"
context.fillStyle = "rgba(0,0,255,0.5)";
context.fillRect(30,30,50,50);
context.strokeRect(30,30,50,50);
//context.fiilRect的第一个和第二个参数代表着以画布的上面为x坐标，左边为y坐标的x,y坐标的值
context.clearRect(40,40,20,20)
//第一个和第二个参数表示的是坐标，第三个和第四个表示的是长宽的大小
// context.beginPath();
context.lineWidth = 10;//线条的宽度
context.lineCap = "round";//线条在最后面的位置
context.moveTo(90,60);//表示线条的末端的位置
context.lineTo(200,20);//表示线条前端的位置
context.stroke();//表示画图
}
</script>
</body>
</html>
