基于SVG的web页面图形绘制API介绍

一：什么是SVG

SVG是1999由W3C发布的2D图形描述语言，纯基于XML格式的标记语言，SVG的

全称是可扩展的矢量图形跟传统的Raster方式的图形(JPG, PNG, GIF等)有很大的差

别。SVG是2D图形开发平台，包括两个部分，一个是基于XML语言的数据描述，另

外一部分是可编程的API，其关键特性支持图形，文本，梯度填充，画笔风格，图形

特效滤镜如高斯模糊，会在稍后的代码中演示。同时还支持各种鼠标事件与DOM部

分API。几乎所有的主流浏览器都支持SVG图形格式的现实与绘制，IE9+以上也开始

支持SVG，在低版本的IE中需要插件支持。

更多了解SVG访问这里：http://www.w3.org/Graphics/SVG/About.html

二：JavaScript中SVG API编程演示

创建与获取SVG对象

// create svg object

var mySvg = document.createElementNS("http://www.w3.org/2000/svg","svg");

mySvg.setAttribute("version","1.2");// IE9+ support SVG 1.1 version

mySvg.setAttribute("baseProfile","tiny");

container.appendChild(mySvg);

在SVG中创建一个矩形图形：

var c1 = document.createElementNS("http://www.w3.org/2000/svg","rect");

c1.setAttribute("x","20");

c1.setAttribute("y","20");

c1.setAttribute("width","150");

c1.setAttribute("height","150");

c1.setAttribute("fill","rgb(0,0,255)");

c1.setAttribute("stroke","rgb(0,0,0)");

c1.setAttribute("stroke-width","4");

mySvg.appendChild(c1);

在SVG中实现文本绘制：

// SVG draw text

var stext = document.createElementNS("http://www.w3.org/2000/svg","text");

stext.setAttribute("x","700");

stext.setAttribute("y","100");

stext.setAttribute("font-size","18px");

stext.setAttribute("fill","#FF0000");

var textString = document.createTextNode("Hello SVG");

stext.appendChild(textString);

mySvg.appendChild(stext);

在SVG对象上实现鼠标点击事件处理与MouseUp事件处理：

// mouse event handling

c1.addEventListener("click",changeColor,false);

c2.addEventListener("mouseup", changeColor,false);

通过SVG 图形滤镜实现高斯模糊：

        <div id="blur-image-demo">
        	<div id="left" style="width:20%;"><img src="woniu.png" alt="Original image" width="325" height="471"></div>
        	<div id="right" style="width:80%;">
		        <svg xmlns="http://www.w3.org/2000/svg" version="1.1">
				  <defs>
				    <filter id="f1" x="0" y="0">
				      <feGaussianBlur in="SourceGraphic" stdDeviation="5" />
				    </filter>
				  </defs>
				  <image x="0" y="0" width="325" height="471" xlink:href="woniu.png" filter="url(#f1)"/>
				</svg>
			</div> 
		</div>

源代码，可以copy直接运行

JavaScript部分

            window.onload = function() {
            	// get DIV
            	var container = document.getElementById("svgContainer");

            	// create svg object
            	var mySvg = document.createElementNS("http://www.w3.org/2000/svg", "svg");
            	mySvg.setAttribute("version", "1.2");// IE9+ support SVG 1.1 version
            	mySvg.setAttribute("baseProfile", "tiny");
            	container.appendChild(mySvg);
            	
            	// create svg shape - rectangle
				var c1 = document.createElementNS("http://www.w3.org/2000/svg", "rect");
            	c1.setAttribute("x", "20");
            	c1.setAttribute("y", "20");
            	c1.setAttribute("width", "150");
            	c1.setAttribute("height", "150");
            	c1.setAttribute("fill", "rgb(0,0,255)");
            	c1.setAttribute("stroke", "rgb(0,0,0)");
            	c1.setAttribute("stroke-width", "4");
            	mySvg.appendChild(c1);
            	
            	// create svg shape - circle
            	var c2 = document.createElementNS("http://www.w3.org/2000/svg", "circle");
            	c2.setAttribute("cx", "250");
            	c2.setAttribute("cy", "100");
            	c2.setAttribute("r", "60");
            	c2.setAttribute("fill", "#996699");
            	c2.setAttribute("stroke", "#AA99FF");
            	c2.setAttribute("stroke-width", "7");
            	mySvg.appendChild(c2);
            	
            	// create svg shape - ellipse
            	var c3 = document.createElementNS("http://www.w3.org/2000/svg", "ellipse");
            	c3.setAttribute("cx", "450");
            	c3.setAttribute("cy", "100");
            	c3.setAttribute("rx", "100");
            	c3.setAttribute("ry", "50");
            	c3.setAttribute("fill", "#FF0000");
            	c3.setAttribute("stroke", "purple");
            	c3.setAttribute("stroke-width", "3");
            	mySvg.appendChild(c3);
            	
            	// create svg shape - draw lines
            	for(var i=0; i<10; i++)
				{
            		var sline = document.createElementNS("http://www.w3.org/2000/svg", "line");
            		var x1 = 580 + i*10;
            		console.log(x1);
            		
            		sline.setAttribute("x1", x1.toString());
            		sline.setAttribute("y1", "10");
            		sline.setAttribute("x2", x1.toString());
            		sline.setAttribute("y2", "180");
            		sline.setAttribute("stroke", "rgb(0,255,0)");
            		sline.setAttribute("stroke-width", "2");
                	mySvg.appendChild(sline);
				}
            	
	        	// SVG draw text
	        	var stext = document.createElementNS("http://www.w3.org/2000/svg", "text");
	        	stext.setAttribute("x", "700");
	        	stext.setAttribute("y", "100");
	        	stext.setAttribute("font-size", "18px");
	        	stext.setAttribute("fill", "#FF0000");
	        	var textString = document.createTextNode("Hello SVG");
	        	stext.appendChild(textString);
	        	mySvg.appendChild(stext);
            	
            	// mouse event handling
            	c1.addEventListener("click", changeColor, false);
            	c2.addEventListener("mouseup", changeColor, false);
            };
            
            function changeColor(evt) {
                var target = evt.target;
                target.setAttributeNS(null, "fill", "green");
            }

<html>
    <head>
        <title>Gloomyfish SVG Demo</title>
        
        <style>
            #svgContainer {
                width:800px;
                height:200px;
                background-color:#EEEEEE;
            }
            
            #left { float: left;} 
			#right { float: right;} 
        </style>       
    </head>
    <body>
        <div id="svgContainer"></div>
        <div id="blur-image-demo">
        	<div id="left" style="width:20%;"><img src="woniu.png" alt="Original image" width="325" height="471"></div>
        	<div id="right" style="width:80%;">
		        <svg xmlns="http://www.w3.org/2000/svg" version="1.1">
				  <defs>
				    <filter id="f1" x="0" y="0">
				      <feGaussianBlur in="SourceGraphic" stdDeviation="5" />
				    </filter>
				  </defs>
				  <image x="0" y="0" width="325" height="471" xlink:href="woniu.png" filter="url(#f1)"/>
				</svg>
			</div> 
		</div>
    </body>
</html>