16.canvas画布控制.html

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>画布控制</title>
	<style type="text/css">
		*{
			padding: 0;
			margin: 0;
		}
		canvas{
			display: block;
			background: #ccc;
			margin: 50px auto;
		}
	</style>
</head>
<body>
	<canvas id="canvas" height="500" width="800"></canvas>
	<script type="text/javascript">
		window.onload = function(){
			var canvas = document.getElementById("canvas");
			var cv = canvas.getContext('2d');

			//画布控制，要放在绘画之前
			
			//画布缩放,横向1.5，竖向0.8
			cv.scale(1.5,0.8);//默认为不旋转为1

			//画布平移，向右50，向下50
			cv.translate(50,50);

			//画布旋转
			cv.rotate(30*(Math.PI/180));

			cv.strokeStyle = "red";
			cv.lineWidth = "5";
			cv.beginPath();//开始路径
			cv.moveTo(40,40);//起点
			cv.lineTo(200,300);//节点1
			cv.lineTo(360,40);
			cv.closePath();//封闭路径
			cv.stroke();//绘制路径
		}
	</script>
</body>
</html>