小强的HTML5移动开发之路（6）——Canvas图形绘制基础_H5之家

在前面提到Canvas是HTML5中一个重要特点，canvas功能非常强大,用photoshop可以实现的效果canvas也同样可以实现，下面我们用canvas实现基本图形的绘制。

一、Canvas标签的使用

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
	</head>
	<body>
		<canvas id="1" width="200" height="200" style="border:1px solid red"></canvas>
	</body>
</html>

可以看到Canvas就像一块画布，我们可以在这个画布上面绘制我们需要的图形。canvas 元素本身是没有绘图能力的。所有的绘制工作必须在 JavaScript 内部完成。

二、画矩形

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
	</head>
	<body>
		<canvas id="1" width="500" height="500" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas>
	</body>
	<script type="text/javascript">
		var c=document.getElementById('1');
		var p=c.getContext("2d");
		//getContext("2d") 对象是内建的 HTML5 对象，拥有多种绘制路径、矩形、圆形、字符以及添加图像的方法。
		p.fillStyle="#FF0000";
		p.fillRect(0, 0, 300, 300);
		p.fillStyle="rgba(0,0,255,0.5)";
		p.fillRect(200,200,500,500);
	</script>
</html>

三、画线条

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">
 </head>
 <body>
	<canvas id="1" width="200" height="200" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas>
 </body>
 <script type="text/javascript">
	var c=document.getElementById('1');
	var p=c.getContext("2d");

	p.moveTo(10,10);
	p.lineTo(150,50);
	p.lineTo(10,50);
	p.stroke();
 </script>
</html>

四、画圆形

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">
 </head>
 <body>
  <canvas id="1" width="200" height="200" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas>
 </body>
  <script type="text/javascript">
	var c=document.getElementById('1');
	var p=c.getContext("2d");

	p.fillStyle="#FF0000";
	p.beginPath();
	p.arc(80,80,15,0,Math.PI*2,true);
	p.closePath();
	p.fill();
 </script>
</html>

五、渐变

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">
 </head>
 <body>
  <canvas id="1" width="200" height="200" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas>
 </body>
  <script type="text/javascript">
	var c=document.getElementById("1");
	var cxt=c.getContext("2d");
	var grd=cxt.createLinearGradient(0,0,175,50);
	grd.addColorStop(0,"#FF0000");
	grd.addColorStop(1,"#00FF00");
	cxt.fillStyle=grd;
	cxt.fillRect(0,0,175,50);
 </script>
</html>

六、绘制图片

<!DOCTYPE HTML>
<html>
<body>

<canvas id="myCanvas" width="200" height="100" style="border:1px solid #c3c3c3;">
Your browser does not support the canvas element.
</canvas>

<script type="text/javascript">

var c=document.getElementById("myCanvas");
var cxt=c.getContext("2d");
var img=new Image()
img.src="/i/eg_flower.png"
cxt.drawImage(img,0,0);

</script>

</body>
</html>

七、多边形

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8">
 </head>
 <body>
  <canvas id="1" width="200" height="200" style="border:1px solid red" onmousemove="mousexy(envent)"></canvas>
 </body>
  <script type="text/javascript">
	var c=document.getElementById('1');
	var p=c.getContext("2d");

	p.fillStyle="#FF0000";
	p.moveTo(10,10);
	p.lineTo(150,50);
	p.lineTo(10,50);
	p.lineTo(20,30);
	p.fill();
 </script>
</html>