js 图片剪裁

深藏阁楼爱情的钟 2022-07-14 06:51 243阅读 0赞

感谢文章：

http://www.w3school.com.cn/cssref/pr\_pos\_clip.asp

http://www.zhangxinxu.com/wordpress/2011/04/css-clip-rect/

尤其要感谢第二篇文章

主要技术是css的clip属性

下面是转载http://www.zhangxinxu.com/wordpress/2011/04/css-clip-rect/  的内容，备份一下：

## CSS clip:rect矩形剪裁功能及一些应用介 ##

### 一、长话短说 ###

CSS中有一个属性叫做`clip`，为修剪，剪裁之意。配合其属性关键字`rect`可以实现元素的矩形裁剪效果。此属性安安稳稳地存在于CSS2.1中，且使用上基本上没有类似于max-height/display:table-cell等浏览器的兼容性问题。但是，貌似大家很少使用此属性。我总结了三点原因：首先是理解上有些门槛；二是其他人使用的不多；三是此属性功能效果有不少替代方案。这种状态有些类似于普通的计算机使用者使用XP系统用得很不错，然后让他去使用Mac系统，可能就会因为使用不习惯、其他人不怎么用、功能XP系统基本都有且支持更广泛而又回到XP系统上。实际上，哪种操作系统更好呢？我想不言而喻。

所以，我们使用overflow实现生硬的剪裁与原生的clip剪裁就有些类似于使用XP系统与Mac般。

老实讲，我自己使用的也不多，仅在两年前在实际项目中解决一些特殊的问题学习并使用了该属性。上个月的“[CSS 相对/绝对(relative/absolute)定位系列（三）][CSS _relative_absolute]”一文中的可用性隐藏部分曾出现了该属性的应用，其作用就是页面元素的可用性隐藏，相关CSS代码如下：

.hidden{
        position:absolute;
        clip: rect(1px 1px 1px 1px); /* IE6, IE7 */
        clip: rect(1px, 1px, 1px, 1px);
    }

根据我自己的测试，貌似上面的第三行CSS是多余的。但是，这里出现是有其理由的，但是自己想不出了个缘由，还望他人指点迷津。

“美特斯邦威，不走寻常路”，正因为似乎大家都忽略了`clip`属性，所以我决定稍稍挖掘下`clip`的属性，让大家开始关注与熟悉此属性。顺带一句，这不是号召关心中华田园犬这种噱头成分颇多的东西，而是实在在的可以在实际项目中大放光彩的东东。

### 二、clip:rect属性亲密接触 ###

根据Dreamweaver的自动提示，`clip`有如下可用属性关键字：  
![clip属性支持的关键字 张鑫旭-鑫空间-鑫生活][clip_ _-_-]

其中，据说继承`inherit`IE浏览器是不支持的，所以该属性就是个酱油帝；然后`"auto"`就是不剪裁之意，除了重置`rect`的作用外，其也是个酱油副帝；所以真正上得了台面张脸的就是`rect(top right bottom left)`，所以，我们下面只讨论`rect(top right bottom left)`这厮。

就顺序上而言，`top → right → bottom → left`，在CSS中是统一相承的，就像是margin的四个值的顺序，border-width等等的四个值顺序——从头顶上开始，顺时针旋转的说~~不过这里的四个值是不可以缩写的。

其中`top right bottom left`表示各个位置的属性值，就像是`width:200px;`中的`200px`，所以，我们会有类似下面的使用：

rect(30px 200px 200px 20px)

那这里的`top right bottom left`究竟指什么的？我们该如何理解呢？

其实是这样的，`top right bottom left`分别指最终剪裁可见区域的上边，右边，下边与左边。而所有的数值都表示位置，且是相对于原始元素的左上角而言的。于是

rect(30px 200px 200px 20px)

表示的含义就是：最终剪裁的矩形的上边距离原始元素的上边缘30像素；剪裁矩形的右边缘距离原元素左边缘的距离是200像素；剪裁矩形的下边缘距离原元素顶部的距离为200像素；剪裁矩形的左边缘距离原元素左边缘的距离时20像素。

上面的表述又长有啰嗦又难以理解，你可以这样想象：饥饿N天的你突然面前出现了块香喷喷的大大的300厘米\*300厘米方形手抓饼，你拔出自己随着携带的锋利的日本刀，在距离顶部30厘米的地方咔嚓一刀，然后在距离左边200厘米的地方咔嚓一刀，然后又以迅雷不及掩耳的速度在距离顶部200厘米和距离20厘米的地方咔嚓一刀。啪啪四刀留下的中间的那块就是剪裁的内容了。所以，您可以将`top right bottom left`理解为在这些位置拿大刀咔咔修剪。

或者理解为在photoshop中为大背景建四个方向的参考线，如下图（300像素\*300像素）所示：

![clip:rect值示意与photoshop参考线 张鑫旭-鑫空间-鑫生活][clip_rect_photoshop_ _-_-]

所谓“一图胜千言，千言不敌一实例”。为了更加直观的理解`clip:rect`后面四个值的含义，我专门做了个demo页面。您可以狠狠地点击这里：[CSS clip:rect几个值含义示意demo][CSS clip_rect_demo]

在demo页面中，我已经将4个值分离出来了，您任意修改其中的一个值，页面上就会出现半透明的黑色层示意这部分内容是将会被剪裁掉的。例如，我们修改第一个值为30，如下图：  
![修改第一个值为30像素 张鑫旭-鑫空间-鑫生活][30_ _-_-]

失去焦点后就会看到图片上出现了改值对应的剪裁作用区域：  
![半透明效果 张鑫旭-鑫空间-鑫生活][_-_-]

类似的，我们修改各个框框的值为30 200 200 20，这时，图片上的效果就是：  
![最后的图片效果 张鑫旭-鑫空间-鑫生活][_-_- 1]

其中图片中未被黑色半透明层覆盖的区域就是最后的剪裁区域，您可以点击下面的“剪裁”按钮确认剪裁：  
![剪裁按钮截图 张鑫旭-鑫空间-鑫生活][_-_- 2]

结果就如下图所示：  
![最后的修剪效果图 张鑫旭-鑫空间-鑫生活][_-_- 3]

您也可以修改其他值做测试的。如果最后图片全部被半透明层覆盖，那么图片最后会被剪裁到一点不剩。

最后有必要说明下：**clip:rect矩形剪裁只能作用于`position:absolute`的元素上**。

### 三、clip:rect矩形剪裁的一些应用介绍 ###

**1. 可用性隐藏**  
根据上面对`top right bottom left`的释义，如果`left >= right`或者`bottom <= top`，则元素会被完全裁掉而不可见，即“隐藏”。通过这种方式隐藏的元素是可以被屏幕阅读器等辅助设备识别的，从而提高了页面的可用性。

例如：

clip: rect(1px 1px 1px 1px); /*left = right, bottom = top*/

或

clip: rect(10px 10px 10px 100px); /*left > right*/

或

clip: rect(100px 10px 10px 10px); /*bottom < top*/

等，正所谓小手抖一抖，剪裁有木有。//zxx:上面几个值的效果您可以去part2部分所提供的[demo页面][CSS clip_rect_demo]做测试滴。

**2. img标签下的CSS Sprite定位**  
为了节约图片资源，我们经常会把小图片整合到一张图片上，称为图片合并技术，国外称为CSS Sprite，含“精灵”之意。然后利用元素区域外`background`内容不可见的特性配合`background-position`定位实现图片的精确显示。

就连万万不能没有的钱都不是万能的，显然，`background-position`下的CSS Sprite定位也不可能适用于各种情况。例如，有时我们希望Sprite图片可以延迟滚动加载，或者是可以很轻松的右键图片另存为...或者是某些特殊的`background-position`属性不起作用的情况。

例如，众所周知的，IE6浏览器不支持Alpha透明通道的png图片（会有蓝蓝的背景），例如下图所示：  
![IE6不支持32位png图片示意 张鑫旭-鑫空间-鑫生活][IE6_32_png_ _-_-]

我们可以使用filter滤镜修复这一问题。然而，如果该png图片以background-image的形式滤镜透明化的话是不支持`background-position`定位的，也就是，我们不可能在IE6下使用background属性实现png图片的Sprite定位。此时，要想实现IE6下png图片的Sprite定位只能在页面上完成，使用img标签，而非`background-image`属性。

然后，img标签下的图片是不会像`background-image`一样元素区域外部分自动隐藏，所以，我们需要借助某些手段对齐进行裁剪，此时`clip:rect`就派上用场了。

您可以狠狠地点击这里：[clip:rect下png图片Sprite定位demo][clip_rect_png_Sprite_demo]

demo页面中的沙发png图片完整显示如下：  
![png sprite图片原图 张鑫旭-鑫空间-鑫生活][png sprite_ _-_-]

如果您手头上的浏览器为IE6浏览器，则打开demo页面会看到如下效果：  
![IE6下demo截图 张鑫旭-鑫空间-鑫生活][IE6_demo_ _-_-]

可以看到鼠标移上去后是有Sprite定位切换实现的hover效果：  
![IE6下png图片hover 张鑫旭-鑫空间-鑫生活][IE6_png_hover _-_-]

可以看到为应用透明滤镜的情况下，使用`img`标签配合`clip:rect`轻松实现了Sprite图片的hover切换效果。这在background属性中也能实现，OK，现在点击下面的“IE6 png透明按钮”，应用`AlphaImageLoader`透明滤镜，然后再鼠标经过，结果也是可以实现hover效果的，见下图：  
![应用filter滤镜后的IE6下hover效果 张鑫旭-鑫空间-鑫生活][filter_IE6_hover_ _-_-]

CSS代码如下：

.clip_a{display:block; width:128px; height:128px;}
    .clip_a img{border:0; position:absolute; clip:rect(0 128px 128px 0);}
    .clip_a:hover{border:0;}
    .clip_a:hover img{margin-top:-128px; clip:rect(128px 128px 256px 0);}

由此可见，CSS Sprite的定位不仅仅可以使用`background`属性，在页面上使用`img`标签，配合`clip:rect`剪裁也是可以轻松实现定位效果的。

**3. 图片剪裁的预览效果**  
关于图像剪裁，很早前我曾翻译过一个名为Jcrop的jQuery插件，文章名为“[jQuery照片图像剪裁插件Jcrop中文翻译详解][jQuery_Jcrop]”，其中有个demo是含有剪裁预览效果的，您可以轻轻地[点击这里][Link 1]访问。

里面的剪裁预览采用margin定位，有着较为复杂的计算。  
![图片预览之margin定位 张鑫旭-鑫空间-鑫生活][margin_ _-_-]

实际上，像剪裁预览效果显示用剪裁属性来实现是最合适的了。于是，自己利用自己先前写的原生态的“[图片旋转+剪裁js插件][js]”中的[zxx.crop\_rotation.js][zxx.crop_rotation.js]写了个图片剪裁预览效果demo。

您可以狠狠地点击这里：[clip:rect图片剪裁效果demo][clip_rect_demo]

demo页面中的旋转可以直接当空气，移动，拖动示意区域，就会在右侧看到对应的剪裁预览效果：  
![剪裁demo效果预览图 张鑫旭-鑫空间-鑫生活][demo_ _-_-]

此例旨在展示clip:rect的潜力，故原理与使用略，您有兴趣可参考上面提到的[文章][js]，以及demo页面相关源代码。

最后记录下文章demo源码的关键代码（不错的剪裁图片的demo）：

##### HTML代码： #####

##### JS代码： #####

其中2个关键的js文件：

zxx.crop\_rotation.js

// zxx.crop_rotation.js by zhangxinxu  welcome to visit my personal website http://www.zhangxinxu.com/
    // 2010-05-06 v1.0 beta
    // 2010-05-07 v1.1 让剪裁box高度随着canvas高度增加而增加
    // 图片剪裁旋转前端展示
    /*一些说明:
    * 1. 旋转效果查看需通过在角度文本框中输入数值
    * 2. 后台处理图片需要5个参数，剪裁起始点，以及剪裁的高宽，这5个参数均可以通过id获取。其中角度值即旋转角度输入框的值，id为zxxRotAngle，坐标及高宽参数分别藏在4个隐藏的文本框中，id分别是：cropPosX, cropPosY, cropImageWidth, cropImageHeight
    * 3. 自动对比当前图片与原始图片尺寸比例，计算实际的剪裁值，对于高度及位置溢出也做了处理
    * 4. 如果出现由于图片旋转而发生遮挡的现象，设置遮挡元素的position属性为relative，z-index为1，可修复此问题
    * 5. 经我测试，excanvas.js需在头部加载以支持IE浏览器的canvas
    */
    var fnImageCropRot = function(o){
    	//o为图片对象
    	if(typeof(o) === "object" && o.tagName.toLowerCase() === "img"){//检测是否是图片类型的DOM对象
    		//当前显示图片的高度和宽度
    		var iCurWidth = o.width, iCurHeight = o.height;
    		o.height = iCurHeight;
    		//获取实际图片的高宽
    		var oCreateImg = new Image();
    		oCreateImg.src = o.src;
    		var iOrigWidth = oCreateImg.width, iOrigHeight = oCreateImg.height;
    		
    		if(iCurWidth && iOrigWidth){//如果宽度为不为0 - 意味着加载成功
    			//计算当前与实际的纵横比
    			var scaleX = iCurWidth / iOrigWidth;
    			var scaleY = iCurHeight / iOrigHeight;			
    			//实现图片对象的包裹
    			//创建包裹div
    			var oRelDiv = document.createElement("div");
    			oRelDiv.style.position = "relative";
    			oRelDiv.style.width = iCurWidth + "px";
    			oRelDiv.style.height = iCurHeight + 30 + "px";
    			oRelDiv.style.top = "30px";
    			//定义ID方法
    			var ID = function(id){
    				return document.getElementById(id);
    			};
    			//插入到当前图片对象之前
    			o.parentNode.insertBefore(oRelDiv, o);
    			//初始化坐标与剪裁高宽
    			var cropW = 80, cropH = 80;
    			var posX = (iCurWidth - cropW)/2, posY = (iCurHeight - cropH)/2;
    			//剪裁需要的HTML元素
    			var sInnerHtml = '<div style="font-size:12px; position:absolute; top:-24px; right:0;">旋转：<input id="zxxRotAngle" type="text" value="0" style="width:38px; height:15px; border:1px solid #a0b3d6; font-size:100%; padding:2px 0 1px 2px; margin-right:3px; color:#333333;" />度</div><canvas id="zxxImageCanvas" style="position:absolute;"></canvas><div id="zxxCropBox" style="height:'+cropH+'px; width:'+cropW+'px; position:absolute; left:'+posX+'px; top:'+posY+'px; border:1px solid black;"><div id="zxxDragBg" style="height:100%; background:white; opacity:0.3; filter:alpha(opacity=30); cursor:move;"></div><div id="dragLeftTop" style="position:absolute; width:4px; height:4px; border:1px solid #000; background:white; overflow:hidden; left:-3px; top:-3px; cursor:nw-resize;"></div><div id="dragLeftBot" style="position:absolute; width:4px; height:4px; border:1px solid #000; background:white; overflow:hidden; left:-3px; bottom:-3px; cursor:sw-resize;"></div><div id="dragRightTop" style="position:absolute; width:4px; height:4px; border:1px solid #000; background:white; overflow:hidden; right:-3px; top:-3px; cursor:ne-resize;"></div><div id="dragRightBot" style="position:absolute; width:4px; height:4px; border:1px solid #000; background:white; overflow:hidden; right:-3px; bottom:-3px; cursor:se-resize;"></div><div id="dragTopCenter" style="position:absolute; width:4px; height:4px; border:1px solid #000; background:white; overflow:hidden; top:-3px; left:50%; margin-left:-3px; cursor:n-resize;"></div><div id="dragBotCenter" style="position:absolute; width:4px; height:4px; border:1px solid #000; background:white; overflow:hidden; bottom:-3px; left:50%; margin-left:-3px; cursor:s-resize;"></div><div id="dragRightCenter" style="position:absolute; width:4px; height:4px; border:1px solid #000; background:white; overflow:hidden; right:-3px; top:50%; margin-top:-3px; cursor:e-resize;"></div><div id="dragLeftCenter" style="position:absolute; width:4px; height:4px; border:1px solid #000; background:white; overflow:hidden; left:-3px; top:50%; margin-top:-3px; cursor:w-resize;"></div></div><input type="hidden" id="cropPosX" value="'+posX/scaleX+'" /><input type="hidden" id="cropPosY" value="'+posY/scaleY+'" /><input type="hidden" id="cropImageWidth" value="'+cropW/scaleX+'" /><input type="hidden" id="cropImageHeight" value="'+cropH/scaleY+'" />';
    			//'
    			//嵌入HTML元素
    			oRelDiv.innerHTML = sInnerHtml;
    			//图片重新插入
    			var oCanvas = ID("zxxImageCanvas");
    			if(window.ActiveXObject && window.G_vmlCanvasManager){
    				//IE
    				oCanvas = window.G_vmlCanvasManager.initElement(oCanvas); //使IE支持动态创建的canvas元素
    			}
    			oRelDiv.insertBefore(o, oCanvas);
    			//---------------------------图片包裹装载完毕-----------------------
    			
    			var fnCanvasRotate = function(canvas,img,rot){//canvas旋转角度的方法
    				//获取图片的高宽
    				var w = iCurWidth;
    				var h = iCurHeight;
    				//角度转为弧度
    				if(!rot){
    					rot = 0;	
    				}
    				var rotation = Math.PI * rot / 180;
    				var c = Math.round(Math.cos(rotation) * 1000) / 1000;
    				var s = Math.round(Math.sin(rotation) * 1000) / 1000;
    				//旋转后canvas标签的大小
    				canvas.height = Math.abs(c*h) + Math.abs(s*w);
    				canvas.width = Math.abs(c*w) + Math.abs(s*h);
    				//绘图开始
    				var context = canvas.getContext("2d");
    				context.save();
    				//改变中心点
    				if (rotation <= Math.PI/2) {
    					context.translate(s*h,0);
    				} else if (rotation <= Math.PI) {
    					context.translate(canvas.width,-c*h);
    				} else if (rotation <= 1.5*Math.PI) {
    					context.translate(-c*w,canvas.height);
    				} else {
    					context.translate(0,-s*w);
    				}
    				//context.translate(canvas.width/2,canvas.height/2);
    				//旋转90°
    
    				context.rotate(rotation);
    				//绘制
    				context.drawImage(img, 0, 0, w, h);
    				context.restore();
    				img.style.display = "none";	
    			};
    			//侦听旋转角度输入框
    			ID("zxxRotAngle").onkeyup = function(){
    				var v = parseInt(this.value, 10);
    				if(!v){
    					v = 0;	
    				}
    				//执行角度旋转
    				fnCanvasRotate(oCanvas, o, v);
    				if(v > 0){
    					oRelDiv.style.height = oCanvas.height + 30 + "px";	
    				}else{
    					oRelDiv.style.height = iCurHeight + 30 + "px";	
    				}
    			};
    			
    			//拖拽与拉伸方法
    			//拖拽拉伸所需参数
    			var params = {
    				left: 0,
    				top: 0,
    				width:0,
    				height:0,
    				currentX: 0,
    				currentY: 0,
    				flag: false,
    				kind: "drag"
    			};
    			//获取相关CSS属性方法
    			var getCss = function(o,key){
    				return o.currentStyle? o.currentStyle[key] : document.defaultView.getComputedStyle(o,false)[key]; 	
    			};
    			var startDrag = function(point, target, kind){	
    				//point是拉伸点，target是被拉伸的目标，其高度及位置会发生改变
    				//此处的target与上面拖拽的target是同一目标，故其params.left,params.top可以共用，也必须共用
    				//初始化宽高
    				params.width = getCss(target, "width");
    				params.height = getCss(target, "height");
    				//初始化坐标
    				if(getCss(target, "left") !== "auto"){
    					params.left = getCss(target, "left");
    				}
    				if(getCss(target, "top") !== "auto"){
    					params.top = getCss(target, "top");
    				}
    				//target是移动对象
    				point.onmousedown = function(event){
    					params.kind = kind;
    					params.flag = true;
    					if(!event){
    						event = window.event;
    					}
    					var e = event;
    					params.currentX = e.clientX;
    					params.currentY = e.clientY;
    					//防止IE文字选中，有助于拖拽平滑
    					point.onselectstart = function(){
    						return false;
    					}
    					return false;  
    				};
    				document.onmouseup = function(){
    					params.flag = false;	
    					if(getCss(target, "left") !== "auto"){
    						params.left = getCss(target, "left");
    					}
    					if(getCss(target, "top") !== "auto"){
    						params.top = getCss(target, "top");
    					}
    					params.width = getCss(target, "width");
    					params.height = getCss(target, "height");
    					
    					//给隐藏文本框赋值
    					posX = parseInt(target.style.left);
    					posY = parseInt(target.style.top);
    					cropW = parseInt(target.style.width);
    					cropH = parseInt(target.style.height);
    					
    					if(posX < 0){
    						posX = 0;	
    					}
    					if(posY < 0){
    						posY = 0;
    					}
    					/*if((posX + cropW) > iCurWidth){
    						cropW = iCurWidth - posX;	
    					}
    					if((posY + cropH) > iCurHeight){
    						cropH = iCurHeight - posY;	
    					}*/
    					
    					
    					//比例计算
    					posX = posX / scaleX;
    					posY /= scaleY;
    					cropW /= scaleX;
    					cropH /= scaleY;
    					//赋值
    					ID("cropPosX").value = posX;
    					ID("cropPosY").value = posY;
    					ID("cropImageWidth").value = cropW;
    					ID("cropImageHeight").value = cropH;
    				};
    				document.onmousemove = function(event){
    					var e = event ? event: window.event;
    					if(params.flag){
    						var nowX = e.clientX, nowY = e.clientY;
    						var disX = nowX - params.currentX, disY = nowY - params.currentY;
    						if(params.kind === "n"){
    							//上拉伸
    							//高度增加或减小，位置上下移动
    							target.style.top = parseInt(params.top) + disY + "px";
    							target.style.height = parseInt(params.height) - disY + "px";
    						}else if(params.kind === "w"){//左拉伸
    							target.style.left = parseInt(params.left) + disX + "px";
    							target.style.width = parseInt(params.width) - disX + "px";
    						}else if(params.kind === "e"){//右拉伸
    							target.style.width = parseInt(params.width) + disX + "px";
    						}else if(params.kind === "s"){//下拉伸
    							target.style.height = parseInt(params.height) + disY + "px";
    						}else if(params.kind === "nw"){//左上拉伸
    							target.style.left = parseInt(params.left) + disX + "px";
    							target.style.width = parseInt(params.width) - disX + "px";
    							target.style.top = parseInt(params.top) + disY + "px";
    							target.style.height = parseInt(params.height) - disY + "px";
    						}else if(params.kind === "ne"){//右上拉伸
    							target.style.top = parseInt(params.top) + disY + "px";
    							target.style.height = parseInt(params.height) - disY + "px";
    							//右
    							target.style.width = parseInt(params.width) + disX + "px";
    						}else if(params.kind === "sw"){//左下拉伸
    							target.style.left = parseInt(params.left) + disX + "px";
    							target.style.width = parseInt(params.width) - disX + "px";
    							//下
    							target.style.height = parseInt(params.height) + disY + "px";
    						}else if(params.kind === "se"){//右下拉伸
    							target.style.width = parseInt(params.width) + disX + "px";
    							target.style.height = parseInt(params.height) + disY + "px";
    						}else{//移动
    							target.style.left = parseInt(params.left) + disX + "px";
    							target.style.top = parseInt(params.top) + disY + "px";
    						}
    					}
    				}	
    			};
    			
    			//绑定拖拽
    			startDrag(ID("zxxDragBg"),ID("zxxCropBox"),"drag");
    			//绑定拉伸
    			startDrag(ID("dragLeftTop"),ID("zxxCropBox"),"nw");
    			startDrag(ID("dragLeftBot"),ID("zxxCropBox"),"sw");
    			startDrag(ID("dragRightTop"),ID("zxxCropBox"),"ne");
    			startDrag(ID("dragRightBot"),ID("zxxCropBox"),"se");
    			startDrag(ID("dragTopCenter"),ID("zxxCropBox"),"n");
    			startDrag(ID("dragBotCenter"),ID("zxxCropBox"),"s");
    			startDrag(ID("dragRightCenter"),ID("zxxCropBox"),"e");
    			startDrag(ID("dragLeftCenter"),ID("zxxCropBox"),"w");
    			
    			//图片不能被选中，目的在于使拖拽顺滑
    			ID("zxxImageCanvas").onselectstart = function(){
    				return false;
    			};
    			o.onselectstart = function(){
    				return false;
    			};
    		}//if end
    	}//if end
    };

excanva.js(你可以去官网下载新的http://excanvas.sourceforge.net/)，使通用浏览器支持HTML5 canvas tag来实现2d绘图

// Copyright 2006 Google Inc.
    //
    // Licensed under the Apache License, Version 2.0 (the "License");
    // you may not use this file except in compliance with the License.
    // You may obtain a copy of the License at
    //
    //   http://www.apache.org/licenses/LICENSE-2.0
    //
    // Unless required by applicable law or agreed to in writing, software
    // distributed under the License is distributed on an "AS IS" BASIS,
    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    // See the License for the specific language governing permissions and
    // limitations under the License.
    
    
    // Known Issues:
    //
    // * Patterns are not implemented.
    // * Radial gradient are not implemented. The VML version of these look very
    //   different from the canvas one.
    // * Clipping paths are not implemented.
    // * Coordsize. The width and height attribute have higher priority than the
    //   width and height style values which isn't correct.
    // * Painting mode isn't implemented.
    // * Canvas width/height should is using content-box by default. IE in
    //   Quirks mode will draw the canvas using border-box. Either change your
    //   doctype to HTML5
    //   (http://www.whatwg.org/specs/web-apps/current-work/#the-doctype)
    //   or use Box Sizing Behavior from WebFX
    //   (http://webfx.eae.net/dhtml/boxsizing/boxsizing.html)
    // * Non uniform scaling does not correctly scale strokes.
    // * Optimize. There is always room for speed improvements.
    
    // Only add this code if we do not already have a canvas implementation
    if (!document.createElement('canvas').getContext) {
    
    (function() {
    
      // alias some functions to make (compiled) code shorter
      var m = Math;
      var mr = m.round;
      var ms = m.sin;
      var mc = m.cos;
      var abs = m.abs;
      var sqrt = m.sqrt;
    
      // this is used for sub pixel precision
      var Z = 10;
      var Z2 = Z / 2;
    
      /**
       * This funtion is assigned to the <canvas> elements as element.getContext().
       * @this {HTMLElement}
       * @return {CanvasRenderingContext2D_}
       */
      function getContext() {
        return this.context_ ||
            (this.context_ = new CanvasRenderingContext2D_(this));
      }
    
      var slice = Array.prototype.slice;
    
      /**
       * Binds a function to an object. The returned function will always use the
       * passed in {@code obj} as {@code this}.
       *
       * Example:
       *
       *   g = bind(f, obj, a, b)
       *   g(c, d) // will do f.call(obj, a, b, c, d)
       *
       * @param {Function} f The function to bind the object to
       * @param {Object} obj The object that should act as this when the function
       *     is called
       * @param {*} var_args Rest arguments that will be used as the initial
       *     arguments when the function is called
       * @return {Function} A new function that has bound this
       */
      function bind(f, obj, var_args) {
        var a = slice.call(arguments, 2);
        return function() {
          return f.apply(obj, a.concat(slice.call(arguments)));
        };
      }
    
      var G_vmlCanvasManager_ = {
        init: function(opt_doc) {
          if (/MSIE/.test(navigator.userAgent) && !window.opera) {
            var doc = opt_doc || document;
            // Create a dummy element so that IE will allow canvas elements to be
            // recognized.
            doc.createElement('canvas');
            doc.attachEvent('onreadystatechange', bind(this.init_, this, doc));
          }
        },
    
        init_: function(doc) {
          // create xmlns
          if (!doc.namespaces['g_vml_']) {
            doc.namespaces.add('g_vml_', 'urn:schemas-microsoft-com:vml',
                               '#default#VML');
    
          }
          if (!doc.namespaces['g_o_']) {
            doc.namespaces.add('g_o_', 'urn:schemas-microsoft-com:office:office',
                               '#default#VML');
          }
    
          // Setup default CSS.  Only add one style sheet per document
          if (!doc.styleSheets['ex_canvas_']) {
            var ss = doc.createStyleSheet();
            ss.owningElement.id = 'ex_canvas_';
            ss.cssText = 'canvas{display:inline-block;overflow:hidden;' +
                // default size is 300x150 in Gecko and Opera
                'text-align:left;width:300px;height:150px}' +
                'g_vml_\\:*{behavior:url(#default#VML)}' +
                'g_o_\\:*{behavior:url(#default#VML)}';
    
          }
    
          // find all canvas elements
          var els = doc.getElementsByTagName('canvas');
          for (var i = 0; i < els.length; i++) {
            this.initElement(els[i]);
          }
        },
    
        /**
         * Public initializes a canvas element so that it can be used as canvas
         * element from now on. This is called automatically before the page is
         * loaded but if you are creating elements using createElement you need to
         * make sure this is called on the element.
         * @param {HTMLElement} el The canvas element to initialize.
         * @return {HTMLElement} the element that was created.
         */
        initElement: function(el) {
          if (!el.getContext) {
    
            el.getContext = getContext;
    
            // Remove fallback content. There is no way to hide text nodes so we
            // just remove all childNodes. We could hide all elements and remove
            // text nodes but who really cares about the fallback content.
            el.innerHTML = '';
    
            // do not use inline function because that will leak memory
            el.attachEvent('onpropertychange', onPropertyChange);
            el.attachEvent('onresize', onResize);
    
            var attrs = el.attributes;
            if (attrs.width && attrs.width.specified) {
              // TODO: use runtimeStyle and coordsize
              // el.getContext().setWidth_(attrs.width.nodeValue);
              el.style.width = attrs.width.nodeValue + 'px';
            } else {
              el.width = el.clientWidth;
            }
            if (attrs.height && attrs.height.specified) {
              // TODO: use runtimeStyle and coordsize
              // el.getContext().setHeight_(attrs.height.nodeValue);
              el.style.height = attrs.height.nodeValue + 'px';
            } else {
              el.height = el.clientHeight;
            }
            //el.getContext().setCoordsize_()
          }
          return el;
        }
      };
    
      function onPropertyChange(e) {
        var el = e.srcElement;
    
        switch (e.propertyName) {
          case 'width':
            el.style.width = el.attributes.width.nodeValue + 'px';
            el.getContext().clearRect();
            break;
          case 'height':
            el.style.height = el.attributes.height.nodeValue + 'px';
            el.getContext().clearRect();
            break;
        }
      }
    
      function onResize(e) {
        var el = e.srcElement;
        if (el.firstChild) {
          el.firstChild.style.width =  el.clientWidth + 'px';
          el.firstChild.style.height = el.clientHeight + 'px';
        }
      }
    
      G_vmlCanvasManager_.init();
    
      // precompute "00" to "FF"
      var dec2hex = [];
      for (var i = 0; i < 16; i++) {
        for (var j = 0; j < 16; j++) {
          dec2hex[i * 16 + j] = i.toString(16) + j.toString(16);
        }
      }
    
      function createMatrixIdentity() {
        return [
          [1, 0, 0],
          [0, 1, 0],
          [0, 0, 1]
        ];
      }
    
      function matrixMultiply(m1, m2) {
        var result = createMatrixIdentity();
    
        for (var x = 0; x < 3; x++) {
          for (var y = 0; y < 3; y++) {
            var sum = 0;
    
            for (var z = 0; z < 3; z++) {
              sum += m1[x][z] * m2[z][y];
            }
    
            result[x][y] = sum;
          }
        }
        return result;
      }
    
      function copyState(o1, o2) {
        o2.fillStyle     = o1.fillStyle;
        o2.lineCap       = o1.lineCap;
        o2.lineJoin      = o1.lineJoin;
        o2.lineWidth     = o1.lineWidth;
        o2.miterLimit    = o1.miterLimit;
        o2.shadowBlur    = o1.shadowBlur;
        o2.shadowColor   = o1.shadowColor;
        o2.shadowOffsetX = o1.shadowOffsetX;
        o2.shadowOffsetY = o1.shadowOffsetY;
        o2.strokeStyle   = o1.strokeStyle;
        o2.globalAlpha   = o1.globalAlpha;
        o2.arcScaleX_    = o1.arcScaleX_;
        o2.arcScaleY_    = o1.arcScaleY_;
        o2.lineScale_    = o1.lineScale_;
      }
    
      function processStyle(styleString) {
        var str, alpha = 1;
    
        styleString = String(styleString);
        if (styleString.substring(0, 3) == 'rgb') {
          var start = styleString.indexOf('(', 3);
          var end = styleString.indexOf(')', start + 1);
          var guts = styleString.substring(start + 1, end).split(',');
    
          str = '#';
          for (var i = 0; i < 3; i++) {
            str += dec2hex[Number(guts[i])];
          }
    
          if (guts.length == 4 && styleString.substr(3, 1) == 'a') {
            alpha = guts[3];
          }
        } else {
          str = styleString;
        }
    
        return {color: str, alpha: alpha};
      }
    
      function processLineCap(lineCap) {
        switch (lineCap) {
          case 'butt':
            return 'flat';
          case 'round':
            return 'round';
          case 'square':
          default:
            return 'square';
        }
      }
    
      /**
       * This class implements CanvasRenderingContext2D interface as described by
       * the WHATWG.
       * @param {HTMLElement} surfaceElement The element that the 2D context should
       * be associated with
       */
      function CanvasRenderingContext2D_(surfaceElement) {
        this.m_ = createMatrixIdentity();
    
        this.mStack_ = [];
        this.aStack_ = [];
        this.currentPath_ = [];
    
        // Canvas context properties
        this.strokeStyle = '#000';
        this.fillStyle = '#000';
    
        this.lineWidth = 1;
        this.lineJoin = 'miter';
        this.lineCap = 'butt';
        this.miterLimit = Z * 1;
        this.globalAlpha = 1;
        this.canvas = surfaceElement;
    
        var el = surfaceElement.ownerDocument.createElement('div');
        el.style.width =  surfaceElement.clientWidth + 'px';
        el.style.height = surfaceElement.clientHeight + 'px';
        el.style.overflow = 'hidden';
        el.style.position = 'absolute';
        surfaceElement.appendChild(el);
    
        this.element_ = el;
        this.arcScaleX_ = 1;
        this.arcScaleY_ = 1;
        this.lineScale_ = 1;
      }
    
      var contextPrototype = CanvasRenderingContext2D_.prototype;
      contextPrototype.clearRect = function() {
        this.element_.innerHTML = '';
      };
    
      contextPrototype.beginPath = function() {
        // TODO: Branch current matrix so that save/restore has no effect
        //       as per safari docs.
        this.currentPath_ = [];
      };
    
      contextPrototype.moveTo = function(aX, aY) {
        var p = this.getCoords_(aX, aY);
        this.currentPath_.push({type: 'moveTo', x: p.x, y: p.y});
        this.currentX_ = p.x;
        this.currentY_ = p.y;
      };
    
      contextPrototype.lineTo = function(aX, aY) {
        var p = this.getCoords_(aX, aY);
        this.currentPath_.push({type: 'lineTo', x: p.x, y: p.y});
    
        this.currentX_ = p.x;
        this.currentY_ = p.y;
      };
    
      contextPrototype.bezierCurveTo = function(aCP1x, aCP1y,
                                                aCP2x, aCP2y,
                                                aX, aY) {
        var p = this.getCoords_(aX, aY);
        var cp1 = this.getCoords_(aCP1x, aCP1y);
        var cp2 = this.getCoords_(aCP2x, aCP2y);
        bezierCurveTo(this, cp1, cp2, p);
      };
    
      // Helper function that takes the already fixed cordinates.
      function bezierCurveTo(self, cp1, cp2, p) {
        self.currentPath_.push({
          type: 'bezierCurveTo',
          cp1x: cp1.x,
          cp1y: cp1.y,
          cp2x: cp2.x,
          cp2y: cp2.y,
          x: p.x,
          y: p.y
        });
        self.currentX_ = p.x;
        self.currentY_ = p.y;
      }
    
      contextPrototype.quadraticCurveTo = function(aCPx, aCPy, aX, aY) {
        // the following is lifted almost directly from
        // http://developer.mozilla.org/en/docs/Canvas_tutorial:Drawing_shapes
    
        var cp = this.getCoords_(aCPx, aCPy);
        var p = this.getCoords_(aX, aY);
    
        var cp1 = {
          x: this.currentX_ + 2.0 / 3.0 * (cp.x - this.currentX_),
          y: this.currentY_ + 2.0 / 3.0 * (cp.y - this.currentY_)
        };
        var cp2 = {
          x: cp1.x + (p.x - this.currentX_) / 3.0,
          y: cp1.y + (p.y - this.currentY_) / 3.0
        };
    
        bezierCurveTo(this, cp1, cp2, p);
      };
    
      contextPrototype.arc = function(aX, aY, aRadius,
                                      aStartAngle, aEndAngle, aClockwise) {
        aRadius *= Z;
        var arcType = aClockwise ? 'at' : 'wa';
    
        var xStart = aX + mc(aStartAngle) * aRadius - Z2;
        var yStart = aY + ms(aStartAngle) * aRadius - Z2;
    
        var xEnd = aX + mc(aEndAngle) * aRadius - Z2;
        var yEnd = aY + ms(aEndAngle) * aRadius - Z2;
    
        // IE won't render arches drawn counter clockwise if xStart == xEnd.
        if (xStart == xEnd && !aClockwise) {
          xStart += 0.125; // Offset xStart by 1/80 of a pixel. Use something
                           // that can be represented in binary
        }
    
        var p = this.getCoords_(aX, aY);
        var pStart = this.getCoords_(xStart, yStart);
        var pEnd = this.getCoords_(xEnd, yEnd);
    
        this.currentPath_.push({type: arcType,
                               x: p.x,
                               y: p.y,
                               radius: aRadius,
                               xStart: pStart.x,
                               yStart: pStart.y,
                               xEnd: pEnd.x,
                               yEnd: pEnd.y});
    
      };
    
      contextPrototype.rect = function(aX, aY, aWidth, aHeight) {
        this.moveTo(aX, aY);
        this.lineTo(aX + aWidth, aY);
        this.lineTo(aX + aWidth, aY + aHeight);
        this.lineTo(aX, aY + aHeight);
        this.closePath();
      };
    
      contextPrototype.strokeRect = function(aX, aY, aWidth, aHeight) {
        var oldPath = this.currentPath_;
        this.beginPath();
    
        this.moveTo(aX, aY);
        this.lineTo(aX + aWidth, aY);
        this.lineTo(aX + aWidth, aY + aHeight);
        this.lineTo(aX, aY + aHeight);
        this.closePath();
        this.stroke();
    
        this.currentPath_ = oldPath;
      };
    
      contextPrototype.fillRect = function(aX, aY, aWidth, aHeight) {
        var oldPath = this.currentPath_;
        this.beginPath();
    
        this.moveTo(aX, aY);
        this.lineTo(aX + aWidth, aY);
        this.lineTo(aX + aWidth, aY + aHeight);
        this.lineTo(aX, aY + aHeight);
        this.closePath();
        this.fill();
    
        this.currentPath_ = oldPath;
      };
    
      contextPrototype.createLinearGradient = function(aX0, aY0, aX1, aY1) {
        var gradient = new CanvasGradient_('gradient');
        gradient.x0_ = aX0;
        gradient.y0_ = aY0;
        gradient.x1_ = aX1;
        gradient.y1_ = aY1;
        return gradient;
      };
    
      contextPrototype.createRadialGradient = function(aX0, aY0, aR0,
                                                       aX1, aY1, aR1) {
        var gradient = new CanvasGradient_('gradientradial');
        gradient.x0_ = aX0;
        gradient.y0_ = aY0;
        gradient.r0_ = aR0;
        gradient.x1_ = aX1;
        gradient.y1_ = aY1;
        gradient.r1_ = aR1;
        return gradient;
      };
    
      contextPrototype.drawImage = function(image, var_args) {
        var dx, dy, dw, dh, sx, sy, sw, sh;
    
        // to find the original width we overide the width and height
        var oldRuntimeWidth = image.runtimeStyle.width;
        var oldRuntimeHeight = image.runtimeStyle.height;
        image.runtimeStyle.width = 'auto';
        image.runtimeStyle.height = 'auto';
    
        // get the original size
        var w = image.width;
        var h = image.height;
    
        // and remove overides
        image.runtimeStyle.width = oldRuntimeWidth;
        image.runtimeStyle.height = oldRuntimeHeight;
    
        if (arguments.length == 3) {
          dx = arguments[1];
          dy = arguments[2];
          sx = sy = 0;
          sw = dw = w;
          sh = dh = h;
        } else if (arguments.length == 5) {
          dx = arguments[1];
          dy = arguments[2];
          dw = arguments[3];
          dh = arguments[4];
          sx = sy = 0;
          sw = w;
          sh = h;
        } else if (arguments.length == 9) {
          sx = arguments[1];
          sy = arguments[2];
          sw = arguments[3];
          sh = arguments[4];
          dx = arguments[5];
          dy = arguments[6];
          dw = arguments[7];
          dh = arguments[8];
        } else {
          throw Error('Invalid number of arguments');
        }
    
        var d = this.getCoords_(dx, dy);
    
        var w2 = sw / 2;
        var h2 = sh / 2;
    
        var vmlStr = [];
    
        var W = 10;
        var H = 10;
    
        // For some reason that I've now forgotten, using divs didn't work
        vmlStr.push(' <g_vml_:group',
                    ' coordsize="', Z * W, ',', Z * H, '"',
                    ' coordorigin="0,0"' ,
                    ' style="width:', W, 'px;height:', H, 'px;position:absolute;');
    
        // If filters are necessary (rotation exists), create them
        // filters are bog-slow, so only create them if abbsolutely necessary
        // The following check doesn't account for skews (which don't exist
        // in the canvas spec (yet) anyway.
    
        if (this.m_[0][0] != 1 || this.m_[0][1]) {
          var filter = [];
    
          // Note the 12/21 reversal
          filter.push('M11=', this.m_[0][0], ',',
                      'M12=', this.m_[1][0], ',',
                      'M21=', this.m_[0][1], ',',
                      'M22=', this.m_[1][1], ',',
                      'Dx=', mr(d.x / Z), ',',
                      'Dy=', mr(d.y / Z), '');
    
          // Bounding box calculation (need to minimize displayed area so that
          // filters don't waste time on unused pixels.
          var max = d;
          var c2 = this.getCoords_(dx + dw, dy);
          var c3 = this.getCoords_(dx, dy + dh);
          var c4 = this.getCoords_(dx + dw, dy + dh);
    
          max.x = m.max(max.x, c2.x, c3.x, c4.x);
          max.y = m.max(max.y, c2.y, c3.y, c4.y);
    
          vmlStr.push('padding:0 ', mr(max.x / Z), 'px ', mr(max.y / Z),
                      'px 0;filter:progid:DXImageTransform.Microsoft.Matrix(',
                      filter.join(''), ", sizingmethod='clip');")
        } else {
          vmlStr.push('top:', mr(d.y / Z), 'px;left:', mr(d.x / Z), 'px;');
        }
    
        vmlStr.push(' ">' ,
                    '<g_vml_:image src="', image.src, '"',
                    ' style="width:', Z * dw, 'px;',
                    ' height:', Z * dh, 'px;"',
                    ' cropleft="', sx / w, '"',
                    ' croptop="', sy / h, '"',
                    ' cropright="', (w - sx - sw) / w, '"',
                    ' cropbottom="', (h - sy - sh) / h, '"',
                    ' />',
                    '</g_vml_:group>');
    
        this.element_.insertAdjacentHTML('BeforeEnd',
                                        vmlStr.join(''));
      };
    
      contextPrototype.stroke = function(aFill) {
        var lineStr = [];
        var lineOpen = false;
        var a = processStyle(aFill ? this.fillStyle : this.strokeStyle);
        var color = a.color;
        var opacity = a.alpha * this.globalAlpha;
    
        var W = 10;
        var H = 10;
    
        lineStr.push('<g_vml_:shape',
                     ' filled="', !!aFill, '"',
                     ' style="position:absolute;width:', W, 'px;height:', H, 'px;"',
                     ' coordorigin="0 0" coordsize="', Z * W, ' ', Z * H, '"',
                     ' stroked="', !aFill, '"',
                     ' path="');
    
        var newSeq = false;
        var min = {x: null, y: null};
        var max = {x: null, y: null};
    
        for (var i = 0; i < this.currentPath_.length; i++) {
          var p = this.currentPath_[i];
          var c;
    
          switch (p.type) {
            case 'moveTo':
              c = p;
              lineStr.push(' m ', mr(p.x), ',', mr(p.y));
              break;
            case 'lineTo':
              lineStr.push(' l ', mr(p.x), ',', mr(p.y));
              break;
            case 'close':
              lineStr.push(' x ');
              p = null;
              break;
            case 'bezierCurveTo':
              lineStr.push(' c ',
                           mr(p.cp1x), ',', mr(p.cp1y), ',',
                           mr(p.cp2x), ',', mr(p.cp2y), ',',
                           mr(p.x), ',', mr(p.y));
              break;
            case 'at':
            case 'wa':
              lineStr.push(' ', p.type, ' ',
                           mr(p.x - this.arcScaleX_ * p.radius), ',',
                           mr(p.y - this.arcScaleY_ * p.radius), ' ',
                           mr(p.x + this.arcScaleX_ * p.radius), ',',
                           mr(p.y + this.arcScaleY_ * p.radius), ' ',
                           mr(p.xStart), ',', mr(p.yStart), ' ',
                           mr(p.xEnd), ',', mr(p.yEnd));
              break;
          }
    
    
          // TODO: Following is broken for curves due to
          //       move to proper paths.
    
          // Figure out dimensions so we can do gradient fills
          // properly
          if (p) {
            if (min.x == null || p.x < min.x) {
              min.x = p.x;
            }
            if (max.x == null || p.x > max.x) {
              max.x = p.x;
            }
            if (min.y == null || p.y < min.y) {
              min.y = p.y;
            }
            if (max.y == null || p.y > max.y) {
              max.y = p.y;
            }
          }
        }
        lineStr.push(' ">');
    
        if (!aFill) {
          var lineWidth = this.lineScale_ * this.lineWidth;
    
          // VML cannot correctly render a line if the width is less than 1px.
          // In that case, we dilute the color to make the line look thinner.
          if (lineWidth < 1) {
            opacity *= lineWidth;
          }
    
          lineStr.push(
            '<g_vml_:stroke',
            ' opacity="', opacity, '"',
            ' joinstyle="', this.lineJoin, '"',
            ' miterlimit="', this.miterLimit, '"',
            ' endcap="', processLineCap(this.lineCap), '"',
            ' weight="', lineWidth, 'px"',
            ' color="', color, '" />'
          );
        } else if (typeof this.fillStyle == 'object') {
          var fillStyle = this.fillStyle;
          var angle = 0;
          var focus = {x: 0, y: 0};
    
          // additional offset
          var shift = 0;
          // scale factor for offset
          var expansion = 1;
    
          if (fillStyle.type_ == 'gradient') {
            var x0 = fillStyle.x0_ / this.arcScaleX_;
            var y0 = fillStyle.y0_ / this.arcScaleY_;
            var x1 = fillStyle.x1_ / this.arcScaleX_;
            var y1 = fillStyle.y1_ / this.arcScaleY_;
            var p0 = this.getCoords_(x0, y0);
            var p1 = this.getCoords_(x1, y1);
            var dx = p1.x - p0.x;
            var dy = p1.y - p0.y;
            angle = Math.atan2(dx, dy) * 180 / Math.PI;
    
            // The angle should be a non-negative number.
            if (angle < 0) {
              angle += 360;
            }
    
            // Very small angles produce an unexpected result because they are
            // converted to a scientific notation string.
            if (angle < 1e-6) {
              angle = 0;
            }
          } else {
            var p0 = this.getCoords_(fillStyle.x0_, fillStyle.y0_);
            var width  = max.x - min.x;
            var height = max.y - min.y;
            focus = {
              x: (p0.x - min.x) / width,
              y: (p0.y - min.y) / height
            };
    
            width  /= this.arcScaleX_ * Z;
            height /= this.arcScaleY_ * Z;
            var dimension = m.max(width, height);
            shift = 2 * fillStyle.r0_ / dimension;
            expansion = 2 * fillStyle.r1_ / dimension - shift;
          }
    
          // We need to sort the color stops in ascending order by offset,
          // otherwise IE won't interpret it correctly.
          var stops = fillStyle.colors_;
          stops.sort(function(cs1, cs2) {
            return cs1.offset - cs2.offset;
          });
    
          var length = stops.length;
          var color1 = stops[0].color;
          var color2 = stops[length - 1].color;
          var opacity1 = stops[0].alpha * this.globalAlpha;
          var opacity2 = stops[length - 1].alpha * this.globalAlpha;
    
          var colors = [];
          for (var i = 0; i < length; i++) {
            var stop = stops[i];
            colors.push(stop.offset * expansion + shift + ' ' + stop.color);
          }
    
          // When colors attribute is used, the meanings of opacity and o:opacity2
          // are reversed.
          lineStr.push('<g_vml_:fill type="', fillStyle.type_, '"',
                       ' method="none" focus="100%"',
                       ' color="', color1, '"',
                       ' color2="', color2, '"',
                       ' colors="', colors.join(','), '"',
                       ' opacity="', opacity2, '"',
                       ' g_o_:opacity2="', opacity1, '"',
                       ' angle="', angle, '"',
                       ' focusposition="', focus.x, ',', focus.y, '" />');
        } else {
          lineStr.push('<g_vml_:fill color="', color, '" opacity="', opacity,
                       '" />');
        }
    
        lineStr.push('</g_vml_:shape>');
    
        this.element_.insertAdjacentHTML('beforeEnd', lineStr.join(''));
      };
    
      contextPrototype.fill = function() {
        this.stroke(true);
      }
    
      contextPrototype.closePath = function() {
        this.currentPath_.push({type: 'close'});
      };
    
      /**
       * @private
       */
      contextPrototype.getCoords_ = function(aX, aY) {
        var m = this.m_;
        return {
          x: Z * (aX * m[0][0] + aY * m[1][0] + m[2][0]) - Z2,
          y: Z * (aX * m[0][1] + aY * m[1][1] + m[2][1]) - Z2
        }
      };
    
      contextPrototype.save = function() {
        var o = {};
        copyState(this, o);
        this.aStack_.push(o);
        this.mStack_.push(this.m_);
        this.m_ = matrixMultiply(createMatrixIdentity(), this.m_);
      };
    
      contextPrototype.restore = function() {
        copyState(this.aStack_.pop(), this);
        this.m_ = this.mStack_.pop();
      };
    
      function matrixIsFinite(m) {
        for (var j = 0; j < 3; j++) {
          for (var k = 0; k < 2; k++) {
            if (!isFinite(m[j][k]) || isNaN(m[j][k])) {
              return false;
            }
          }
        }
        return true;
      }
    
      function setM(ctx, m, updateLineScale) {
        if (!matrixIsFinite(m)) {
          return;
        }
        ctx.m_ = m;
    
        if (updateLineScale) {
          // Get the line scale.
          // Determinant of this.m_ means how much the area is enlarged by the
          // transformation. So its square root can be used as a scale factor
          // for width.
          var det = m[0][0] * m[1][1] - m[0][1] * m[1][0];
          ctx.lineScale_ = sqrt(abs(det));
        }
      }
    
      contextPrototype.translate = function(aX, aY) {
        var m1 = [
          [1,  0,  0],
          [0,  1,  0],
          [aX, aY, 1]
        ];
    
        setM(this, matrixMultiply(m1, this.m_), false);
      };
    
      contextPrototype.rotate = function(aRot) {
        var c = mc(aRot);
        var s = ms(aRot);
    
        var m1 = [
          [c,  s, 0],
          [-s, c, 0],
          [0,  0, 1]
        ];
    
        setM(this, matrixMultiply(m1, this.m_), false);
      };
    
      contextPrototype.scale = function(aX, aY) {
        this.arcScaleX_ *= aX;
        this.arcScaleY_ *= aY;
        var m1 = [
          [aX, 0,  0],
          [0,  aY, 0],
          [0,  0,  1]
        ];
    
        setM(this, matrixMultiply(m1, this.m_), true);
      };
    
      contextPrototype.transform = function(m11, m12, m21, m22, dx, dy) {
        var m1 = [
          [m11, m12, 0],
          [m21, m22, 0],
          [dx,  dy,  1]
        ];
    
        setM(this, matrixMultiply(m1, this.m_), true);
      };
    
      contextPrototype.setTransform = function(m11, m12, m21, m22, dx, dy) {
        var m = [
          [m11, m12, 0],
          [m21, m22, 0],
          [dx,  dy,  1]
        ];
    
        setM(this, m, true);
      };
    
      /******** STUBS ********/
      contextPrototype.clip = function() {
        // TODO: Implement
      };
    
      contextPrototype.arcTo = function() {
        // TODO: Implement
      };
    
      contextPrototype.createPattern = function() {
        return new CanvasPattern_;
      };
    
      // Gradient / Pattern Stubs
      function CanvasGradient_(aType) {
        this.type_ = aType;
        this.x0_ = 0;
        this.y0_ = 0;
        this.r0_ = 0;
        this.x1_ = 0;
        this.y1_ = 0;
        this.r1_ = 0;
        this.colors_ = [];
      }
    
      CanvasGradient_.prototype.addColorStop = function(aOffset, aColor) {
        aColor = processStyle(aColor);
        this.colors_.push({offset: aOffset,
                           color: aColor.color,
                           alpha: aColor.alpha});
      };
    
      function CanvasPattern_() {}
    
      // set up externs
      G_vmlCanvasManager = G_vmlCanvasManager_;
      CanvasRenderingContext2D = CanvasRenderingContext2D_;
      CanvasGradient = CanvasGradient_;
      CanvasPattern = CanvasPattern_;
    
    })();
    
    } // if

代码已经上传到资源了，哎还要审核。。。。算了，不发资源地址了

[CSS _relative_absolute]: http://www.zhangxinxu.com/wordpress/?p=1528
[clip_ _-_-]: /images/20220714/2186c033d4a64921b599e4f517e325ad.png
[clip_rect_photoshop_ _-_-]: /images/20220714/e76a4a14816542e389fd43b06c4dce38.png
[CSS clip_rect_demo]: http://www.zhangxinxu.com/study/201103/css-rect-demo.html
[30_ _-_-]: /images/20220714/ec218fbb3aca49b4a5f1cd8eff5a8a9e.png
[_-_-]: /images/20220714/64f5c13a6be2457bba2f82e2965be6df.png
[_-_- 1]: /images/20220714/f5d406c8243840a6be04001153081372.png
[_-_- 2]: /images/20220714/3b132adacff7423ca253b01034a9a4b2.png
[_-_- 3]: /images/20220714/27e9943554d5411a8f55a963e8ceb803.png
[IE6_32_png_ _-_-]: /images/20220714/5fd81a475f664366aaf4da8618e43380.png
[clip_rect_png_Sprite_demo]: http://www.zhangxinxu.com/study/201104/css-rect-img-sprite-png.html
[png sprite_ _-_-]: /images/20220714/62d0e30e09744c969dda47946c5c7f08.png
[IE6_demo_ _-_-]: /images/20220714/1c6f39759d044c8495cf3c0fb4e0a55b.png
[IE6_png_hover _-_-]: /images/20220714/9b6259ab40194a1895c50104cb6c8048.png
[filter_IE6_hover_ _-_-]: /images/20220714/0fe2bdaac31e4929b88f6e1901a1ed97.png
[jQuery_Jcrop]: http://www.zhangxinxu.com/wordpress/?p=359
[Link 1]: http://www.zhangxinxu.com/jq/jcrop_zh/demo/example3.html
[margin_ _-_-]: /images/20220714/71c1702c3e194127beb582e870132c07.png
[js]: http://www.zhangxinxu.com/wordpress/?p=804
[zxx.crop_rotation.js]: http://www.zhangxinxu.com/study/js/zxx.crop_rotation.js
[clip_rect_demo]: http://www.zhangxinxu.com/study/201104/css-rect-img-preview.html
[demo_ _-_-]: /images/20220714/90196bf8273849978be9cc2e323e1fb8.png