切图js

首先引用一段关于拖动，缩放，剪切的基础代码

 /*
 *    作者：http://cloudgamer.cnblogs.com/
 *
 *    改进与增强
 *    作者：http://yoker.sc0826.com/
 *    时间：2008年11月09日
 *    功能：远程web图片在线裁剪，图片预加载比例缩放，裁剪参数个性设置，裁剪比例缩放等。
 */

 /* -------------这里定义一些环境变量--------------- */

 //获取dom对象的方法
 var $ = function(id) {
     return "string" == typeof id ? document.getElementById(id) : id;
 };
 //判断是否ie
 var isIE = (document.all) ? true : false;
 //添加事件
 function addEventHandler(oTarget, sEventType, fnHandler) {
     if (oTarget.addEventListener) {
         oTarget.addEventListener(sEventType, fnHandler, false);
     } else if (oTarget.attachEvent) {
         oTarget.attachEvent("on" + sEventType, fnHandler);
     } else {
         oTarget["on" + sEventType] = fnHandler;
     }
 };
 //移除事件
 function removeEventHandler(oTarget, sEventType, fnHandler) {
     if (oTarget.removeEventListener) {
         oTarget.removeEventListener(sEventType, fnHandler, false);
     } else if (oTarget.detachEvent) {
         oTarget.detachEvent("on" + sEventType, fnHandler);
     } else {
         oTarget["on" + sEventType] = null;
     }
 };
 //这相当于一个类工厂。
 //js中函数即是类，new function()就是用该函数作为构造函数生成一个对象
 //当然，默认的该对象需自定义一个initialize方法
 var Class = {
     create: function() {
         return function() {
             this.initialize.apply(this, arguments);
         }
     }
 }

 //这是对象拷贝函数
 Object.extend = function(destination, source) {
     for (var property in source) {
         destination[property] = source[property];
     }
     return destination;
 }

环境变量

这里定义了几个环境变量，包括挂载/卸载事件方法，根据id获取dom对象方法。比较有意思的是

var Class = {
create: function() {
return function() {
this.initialize.apply(this, arguments);
}
}
}

的写法。网上说prototype.js是这么写的。

看起来这样写实现了某种标准化，比如能产生一批受约束的类，这些类看起来是从某个抽象类中继承而来，然后更方便的用propertype定义方法。

整个编程看起来更加面向对象而不是面向函数。

除此之外没什么好处。

js的prototype相当于c#的直接初始化字段，function相当于在构造函数中初始化字段，无形中都生成对象。js中的this应是某个对象，

 //拖放程序
 var Drag = Class.create();
 Drag.prototype = {
     //拖放对象,触发对象
     initialize: function(obj, drag, options) {
         var oThis = this;

         this._obj = $(obj); //拖放对象
         this.Drag = $(drag); //触发对象
         this._x = this._y = 0; //记录鼠标相对拖放对象的位置
         //事件对象(用于移除事件)
         this._fM = function(e) { oThis.Move(window.event || e); }
         this._fS = function() { oThis.Stop(); }

         this.SetOptions(options);

         this.Limit = !!this.options.Limit;
         this.mxLeft = parseInt(this.options.mxLeft);
         this.mxRight = parseInt(this.options.mxRight);
         this.mxTop = parseInt(this.options.mxTop);
         this.mxBottom = parseInt(this.options.mxBottom);

         this.onMove = this.options.onMove;

         this._obj.style.position = "absolute";
         addEventHandler(this.Drag, "mousedown", function(e) { oThis.Start(window.event || e); });
     },
     //设置默认属性
     SetOptions: function(options) {
         this.options = {//默认值
             Limit: false, //是否设置限制(为true时下面参数有用,可以是负数)
             mxLeft: 0, //左边限制
             mxRight: 0, //右边限制
             mxTop: 0, //上边限制
             mxBottom: 0, //下边限制
             onMove: function() { } //移动时执行
         };
         Object.extend(this.options, options || {});
     },
     //准备拖动
     Start: function(oEvent) {
         //记录鼠标相对拖放对象的位置
         this._x = oEvent.clientX - this._obj.offsetLeft;
         this._y = oEvent.clientY - this._obj.offsetTop;
         //mousemove时移动 mouseup时停止
         addEventHandler(document, "mousemove", this._fM);
         addEventHandler(document, "mouseup", this._fS);
         //使鼠标移到窗口外也能释放
         if (isIE) {
             addEventHandler(this.Drag, "losecapture", this._fS);
             this.Drag.setCapture();
         } else {
             addEventHandler(window, "blur", this._fS);
         }
     },
     //拖动
     Move: function(oEvent) {
         //清除选择(ie设置捕获后默认带这个)
         window.getSelection && window.getSelection().removeAllRanges();
         //当前鼠标位置减去相对拖放对象的位置得到offset位置
         var iLeft = oEvent.clientX - this._x, iTop = oEvent.clientY - this._y;
         //设置范围限制
         if (this.Limit) {
             //获取超出长度
             var iRight = iLeft + this._obj.offsetWidth - this.mxRight, iBottom = iTop + this._obj.offsetHeight - this.mxBottom;
             //这里是先设置右边下边再设置左边上边,可能会不准确
             if (iRight > 0) iLeft -= iRight;
             if (iBottom > 0) iTop -= iBottom;
             if (this.mxLeft > iLeft) iLeft = this.mxLeft;
             if (this.mxTop > iTop) iTop = this.mxTop;
         }
         //设置位置
         this._obj.style.left = iLeft + "px";
         this._obj.style.top = iTop + "px";
         //附加程序
         this.onMove();
     },
     //停止拖动
     Stop: function() {
         //移除事件
         removeEventHandler(document, "mousemove", this._fM);
         removeEventHandler(document, "mouseup", this._fS);
         if (isIE) {
             removeEventHandler(this.Drag, "losecapture", this._fS);
             this.Drag.releaseCapture();
         } else {
             removeEventHandler(window, "blur", this._fS);
         }
     }
 };

拖放类

拖放类的基本思路是给一个参照的dom对象，一个移动的dom对象，捕捉鼠标相对参照对象的变化，赋值给移动对象。

另外两个功能，其一允许用户自定义onmove,把移动中x,y值传出去，其二给移动对象定义mouseclik确保鼠标按下时记录相关参数，做好拖放准备。

总之是拖放功能的总管秘书。

缩放类

与拖放类思路基本相同。

document.defaultView.getComputedStyle用于获取所有dom元素的style对象。

 //图片切割
 var ImgCropper = Class.create();
 ImgCropper.prototype = {
     //容器对象,拖放缩放对象,图片地址,宽度,高度
     initialize: function(container, drag, url, width, height, options) {
         var oThis = this;

         //容器对象
         this.Container = $(container);
         this.Container.style.position = "relative";
         this.Container.style.overflow = "hidden";

         //拖放对象
         this.Drag = $(drag);
         this.Drag.style.cursor = "move";
         this.Drag.style.zIndex = 200;
         if (isIE) {
             //设置overflow解决ie6的渲染问题(缩放时填充对象高度的问题)
             this.Drag.style.overflow = "hidden";
             //ie下用一个透明的层填充拖放对象 不填充的话onmousedown会失效(未知原因)
             (function(style) {
                 style.width = style.height = "100%";
                 style.backgroundColor = "#fff";
                 style.opacity = 0;
                 style.filter = 'alpha(opacity = 0)';
             })(this.Drag.appendChild(document.createElement("div")).style)
         }

         this._cropper = this.Container.appendChild(document.createElement("img")); //切割对象
         this._pic = this.Container.appendChild(document.createElement("img")); //图片对象
         this._pic.style.position = "absolute";
         this._cropper.style.position = "absolute";
         this._pic.style.top = this._pic.style.left = this._cropper.style.top = this._cropper.style.left = "0"; //对齐
         this._pic.style.zIndex = 100;
         this._cropper.style.zIndex = 150;
         this._cropper.onload = function() { oThis.SetPos(); }

         this.Url = url; //图片地址
         this.Width = parseInt(width); //宽度
         this.Height = parseInt(height); //高度

         this.SetOptions(options);

         this.Opacity = parseInt(this.options.Opacity);
         this.dragTop = parseInt(this.options.dragTop);
         this.dragLeft = parseInt(this.options.dragLeft);
         this.dragWidth = parseInt(this.options.dragWidth);
         this.dragHeight = parseInt(this.options.dragHeight);

         //设置预览对象
         this.View = $(this.options.View) || null; //预览对象
         this.viewWidth = parseInt(this.options.viewWidth);
         this.viewHeight = parseInt(this.options.viewHeight);
         this._view = null; //预览图片对象
         if (this.View) {
             this.View.style.position = "relative";
             this.View.style.overflow = "hidden";
             this._view = this.View.appendChild(document.createElement("img"));
             this._view.style.position = "absolute";
         }

         this.Scale = parseInt(this.options.Scale);

         //设置拖放
         this._drag = new Drag(this.Drag, this.Drag, { Limit: true, onMove: function() { oThis.SetPos(); } });
         //设置缩放
         this._resize = this.GetResize();
         this.Init();
     },
     //设置默认属性
     SetOptions: function(options) {
         this.options = {//默认值
             Opacity: 50, //透明度(0到100)
             //拖放位置和宽高
             dragTop: 0,
             dragLeft: 0,
             dragWidth: 100,
             dragHeight: 100,
             //缩放触发对象
             Right: "",
             Left: "",
             Up: "",
             Down: "",
             RightDown: "",
             LeftDown: "",
             RightUp: "",
             LeftUp: "",
             Scale: false, //是否按比例缩放
             //预览对象设置
             View: "", //预览对象
             viewWidth: 100, //预览宽度
             viewHeight: 100//预览高度
         };
         Object.extend(this.options, options || {});
     },
     //初始化对象
     Init: function() {
         var oThis = this;

         //设置拖放对象
         this.Drag.style.top = this.dragTop + "px";
         this.Drag.style.left = this.dragLeft + "px";
         this.Drag.style.width = this.dragWidth + "px";
         this.Drag.style.height = this.dragHeight + "px";

         //Yoker.Wu前台缩放效果改善，图片加载完成后，得到缩放大小再初始化显示
         var trueImg = new Image();
         trueImg.src = this.Url;
         //图片已经加载并缓存
         if (trueImg.complete) {
             if (trueImg.width > oThis.Width || trueImg.height > oThis.Height) {
                 if (this.Width / this.Height > trueImg.width / trueImg.height) {
                     this.Width = parseInt(trueImg.width * this.Height / trueImg.height);
                 } else {
                     this.Height = parseInt(trueImg.height * this.Width / trueImg.width);
                 }
             } else {
                 this.Width = trueImg.width;
                 this.Height = trueImg.height;
             }

             //设置容器
             this.Container.style.width = this.Width + "px";
             this.Container.style.height = this.Height + "px";

             //设置切割对象
             this._cropper.src = this.Url;
             this._pic.src = this.Url;
             this._pic.style.width = this._cropper.style.width = this.Width + "px";
             this._pic.style.height = this._cropper.style.height = this.Height + "px";
             if (isIE) {
                 if (navigator.appVersion.indexOf("MSIE 6.0") != -1
                 || navigator.appVersion.indexOf("MSIE 7.0") != -1
                 || navigator.appVersion.indexOf("MSIE 8.0") != -1) {
                     this._pic.style.filter = "alpha(opacity:" + this.Opacity + ")";
                 }
                 else if (navigator.appVersion.indexOf("MSIE 9.0") != -1) {
                     this._pic.style.filter = "alpha(opacity:" + this.Opacity + ")";
                     this._pic.style.opacity = this.Opacity / 100;
                 }
                 else {
                     this._pic.style.opacity = this.Opacity / 100;
                 }
             } else {
                 this._pic.style.opacity = this.Opacity / 100;
             }
             this._cropper.style.filter = "alpha(opacity:100)";
             this._cropper.style.opacity = 1;
             //设置预览对象
             if (this.View) { this._view.src = this.Url; }

             //设置拖放
             this._drag.mxRight = this.Width; this._drag.mxBottom = this.Height;
             //设置缩放
             if (this._resize) { this._resize.mxRight = this.Width; this._resize.mxBottom = this.Height; this._resize.Scale = this.Scale; }
         }
         //新加载的情况
         trueImg.onload = function() {
             if (this.width > oThis.Width || this.height > oThis.Height) {
                 if (oThis.Width / oThis.Height > this.width / this.height) {
                     oThis.Width = parseInt(this.width * oThis.Height / this.height);
                 } else {
                     oThis.Height = parseInt(this.height * oThis.Width / this.width);
                 }
             } else {
                 oThis.Width = this.width;
                 oThis.Height = this.height;
             }
             //设置容器
             oThis.Container.style.width = oThis.Width + "px";
             oThis.Container.style.height = oThis.Height + "px";

             //设置切割对象
             oThis._cropper.src = oThis.Url;
             oThis._pic.src = oThis.Url;
             oThis._pic.style.width = oThis._cropper.style.width = oThis.Width + "px";
             oThis._pic.style.height = oThis._cropper.style.height = oThis.Height + "px";
             if (isIE) {
                 if (navigator.appVersion.indexOf("MSIE 6.0") != -1
                 || navigator.appVersion.indexOf("MSIE 7.0") != -1
                 || navigator.appVersion.indexOf("MSIE 8.0") != -1) {
                     oThis._pic.style.filter = "alpha(opacity:" + oThis.Opacity + ")";
                 }
                 else if (navigator.appVersion.indexOf("MSIE 9.0") != -1) {
                     oThis._pic.style.filter = "alpha(opacity:" + oThis.Opacity + ")";
                     oThis._pic.style.opacity = oThis.Opacity / 100;
                 }
                 else {
                     oThis._pic.style.opacity = oThis.Opacity / 100;
                 }
             } else {
                 oThis._pic.style.opacity = oThis.Opacity / 100;
             }
             oThis._cropper.style.filter = "alpha(opacity:100)";
             oThis._cropper.style.opacity = 1;

             //设置预览对象
             if (oThis.View) { oThis._view.src = oThis.Url; }

             //设置拖放
             oThis._drag.mxRight = oThis.Width; oThis._drag.mxBottom = oThis.Height;
             //设置缩放
             if (oThis._resize) { oThis._resize.mxRight = oThis.Width; oThis._resize.mxBottom = oThis.Height; oThis._resize.Scale = oThis.Scale; }
         }
     },
     //设置获取缩放对象
     GetResize: function() {
         var op = this.options;
         //有触发对象时才设置
         if (op.RightDown || op.LeftDown || op.RightUp || op.LeftUp || op.Right || op.Left || op.Up || op.Down) {
             var oThis = this, _resize = new Resize(this.Drag, { Limit: true, onResize: function() { oThis.SetPos(); } });

             //设置缩放触发对象
             if (op.RightDown) { _resize.Set(op.RightDown, "right-down"); }
             if (op.LeftDown) { _resize.Set(op.LeftDown, "left-down"); }

             if (op.RightUp) { _resize.Set(op.RightUp, "right-up"); }
             if (op.LeftUp) { _resize.Set(op.LeftUp, "left-up"); }

             if (op.Right) { _resize.Set(op.Right, "right"); }
             if (op.Left) { _resize.Set(op.Left, "left"); }

             if (op.Up) { _resize.Set(op.Up, "up"); }
             if (op.Down) { _resize.Set(op.Down, "down"); }

             return _resize;
         } else { return null; }
     },
     //设置切割
     SetPos: function() {
         var o = this.Drag;
         //按拖放对象的参数进行切割
         this._cropper.style.clip = "rect(" + o.offsetTop + "px " + (o.offsetLeft + o.offsetWidth) + "px " + (o.offsetTop + o.offsetHeight) + "px " + o.offsetLeft + "px)";

         //切割预览
         if (this.View) this.PreView();
     },
     //切割预览
     PreView: function() {
         //按比例设置宽度和高度
         var o = this.Drag, h = this.viewWidth, w = h * o.offsetWidth / o.offsetHeight;
         if (w > this.viewHeight) { w = this.viewHeight; h = w * o.offsetHeight / o.offsetWidth; }
         //获取对应比例尺寸
         var scale = h / o.offsetHeight, ph = this.Height * scale, pw = this.Width * scale, pt = o.offsetTop * scale, pl = o.offsetLeft * scale, styleView = this._view.style;
         //设置样式
         styleView.width = pw + "px"; styleView.height = ph + "px";
         styleView.top = -pt + "px "; styleView.left = -pl + "px";
         //切割预览图
         styleView.clip = "rect(" + pt + "px " + (pl + w) + "px " + (pt + h) + "px " + pl + "px)";
     }
 }

切割类

拖放中 window.getSelection && window.getSelection().removeAllRanges();用途不明，待查。

缩放中防止冒泡用户不明。