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;
}

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。

 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)";
    }
}

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。