25.canvas绘制图片.html

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>canvas绘制图片</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>
	<img id='pic' src="./file/p.png" hidden>
	<script type="text/javascript">
		window.onload = function(){
			var canvas = document.getElementById("canvas");
			var cv = canvas.getContext('2d');
			var pic = document.getElementById("pic");

			//必须得图片载入完成后才能写入到canvas中,如果不在window.onload中那么就得在图片.onload中画图。
			
			cv.drawImage(pic,10,10);
			
			//除载入已有图片还可以动态载入图片
			var newimg = document.createElement("img");
			newimg.src = "./file/p.png";
			// drawImage("图像资源",裁切开始x位置，裁切开始y位置，宽，高，放置到x位置，放置到y位置,放置后款，放置后高)
			cv.drawImage(newimg,50,100,100,50,300,300,100,50);
	

			
		}
	</script>
</body>
</html>