HTML5 Canvas阴影用法演示和代码详情-H5教程-PHP中文网

HTML5 Canvas阴影用法演示和代码详情

黄舟

发布： 2017-03-03 16:02:20

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html5 canvas阴影用法演示

HTML5 Canvas中提供了设置阴影的四个属性值分别为：

context.shadowColor = “red” 表示设置阴影颜色为红色

context.shadowOffsetX = 0表示阴影相对TEXT的水平距离，0表示两者水平位置重合

context.shadowOffsetY = 0表示阴影相对TEXT的垂直距离，0表示两者垂直位置重合

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context.shadowBlur = 10 阴影模糊效果，值越大模糊越厉害。

一个最简单的带有阴影的矩形代码如下：

context.shadowColor = "RGBA(127,127,127,1)";
context.shadowOffsetX = 3;
context.shadowOffsetY = 3;
context.shadowBlur = 0;
context.fillStyle = "RGBA(0, 0, 0, 0.8)";  
context.fillRect(10, hh+10, 200,canvas.height/4-20);

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效果如下：

阴影文字：

只要设置shadowOffsetX与shadowOffsetY的值，当值都正数时，阴影相对文字的右下

方偏移。当值都为负数时，阴影相对文字的左上方偏移。

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3D拉影效果：

在同一位置不断的重复绘制文字同时改变shadowOffsetX、shadowOffsetY、shadowBlur

的值，从小到大不断偏移不断增加，透明度也不断增加。就得到了拉影效果文字。

边缘模糊效果文字：

在3D拉影效果的基础上在四个方向重复，就得到了边缘羽化的文字效果。

运行效果：

程序代码：

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="X-UA-Compatible" content="chrome=IE8">
<meta http-equiv="Content-type" content="text/html;charset=UTF-8">
<title>Canvas Clip Demo</title>
<link href="default.css" rel="stylesheet" />
	<script>
		var ctx = null; // global variable 2d context
		var imageTexture = null;
		window.onload = function() {
			var canvas = document.getElementById("text_canvas");
			console.log(canvas.parentNode.clientWidth);
			canvas.width = canvas.parentNode.clientWidth;
			canvas.height = canvas.parentNode.clientHeight;
			
			if (!canvas.getContext) {
			    console.log("Canvas not supported. Please install a HTML5 compatible browser.");
			    return;
			}
			var context = canvas.getContext('2d');
			
			// section one - shadow and blur
			context.fillStyle="black";
			context.fillRect(0, 0, canvas.width, canvas.height/4);
			context.font = '60pt Calibri';
			
			context.shadowColor = "white";
			context.shadowOffsetX = 0;
			context.shadowOffsetY = 0;
			context.shadowBlur = 20;
			context.fillText("Blur Canvas", 40, 80);
			context.strokeStyle = "RGBA(0, 255, 0, 1)";
			context.lineWidth = 2;
			context.strokeText("Blur Canvas", 40, 80);
			
			// section two - shadow font
			var hh = canvas.height/4;
			context.fillStyle="white";
			context.fillRect(0, hh, canvas.width, canvas.height/4);
			context.font = '60pt Calibri';
			
			context.shadowColor = "RGBA(127,127,127,1)";
			context.shadowOffsetX = 3;
			context.shadowOffsetY = 3;
			context.shadowBlur = 0;
			context.fillStyle = "RGBA(0, 0, 0, 0.8)";
			context.fillText("Blur Canvas", 40, 80+hh);
			
			// section three - down shadow effect
			var hh = canvas.height/4 + hh;
			context.fillStyle="black";
			context.fillRect(0, hh, canvas.width, canvas.height/4);
			for(var i = 0; i < 10; i++)
			{
				context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
				context.shadowOffsetX = i*2;
				context.shadowOffsetY = i*2;
				context.shadowBlur = i*2;
				context.fillStyle = "RGBA(127, 127, 127, 1)";
				context.fillText("Blur Canvas", 40, 80+hh);
			}
			
			// section four -  fade effect
			var hh = canvas.height/4 + hh;
			context.fillStyle="green";
			context.fillRect(0, hh, canvas.width, canvas.height/4);
			for(var i = 0; i < 10; i++)
			{
				context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
				context.shadowOffsetX = 0;
				context.shadowOffsetY = -i*2;
				context.shadowBlur = i*2;
				context.fillStyle = "RGBA(127, 127, 127, 1)";
				context.fillText("Blur Canvas", 40, 80+hh);
			}
			for(var i = 0; i < 10; i++)
			{
				context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
				context.shadowOffsetX = 0;
				context.shadowOffsetY = i*2;
				context.shadowBlur = i*2;
				context.fillStyle = "RGBA(127, 127, 127, 1)";
				context.fillText("Blur Canvas", 40, 80+hh);
			}
			for(var i = 0; i < 10; i++)
			{
				context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
				context.shadowOffsetX = i*2;
				context.shadowOffsetY = 0;
				context.shadowBlur = i*2;
				context.fillStyle = "RGBA(127, 127, 127, 1)";
				context.fillText("Blur Canvas", 40, 80+hh);
			}
			for(var i = 0; i < 10; i++)
			{
				context.shadowColor = "RGBA(255, 255, 255," + ((10-i)/10) + ")";
				context.shadowOffsetX = -i*2;
				context.shadowOffsetY = 0;
				context.shadowBlur = i*2;
				context.fillStyle = "RGBA(127, 127, 127, 1)";
				context.fillText("Blur Canvas", 40, 80+hh);
			}
		}
		
	</script>
</head>
<body>
	<h1>HTML5 Canvas Clip Demo - By Gloomy Fish</h1>
	<pre>Fill And Stroke Clip</pre>
	<p id="my_painter">
		<canvas id="text_canvas"></canvas>
	</p>
</body>
</html>

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