JavaScript 图片截取效果

var isIE = (document.all) ? true : false;

var isIE6 = isIE && ([/MSIE (\d)\.0/i.(navigator.userAgent)][0][1] == 6);

var $ = function (id) {
	return "string" == typeof id ? document.getElementById(id) : id;
};

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

var Extend = function(destination, source) {
	for (var property in source) {
		destination[property] = source[property];
	}
}

var Bind = function(object, fun) {
	return function() {
		return fun.apply(object, arguments);
	}
}

var BindAsEventListener = function(object, fun) {
	var args = Array.prototype.slice.call(arguments).slice(2);
	return function(event) {
		return fun.apply(object, [event || window.event].concat(args));
	}
}

var CurrentStyle = function(element){
	return element.currentStyle || document.defaultView.getComputedStyle(element, null);
}

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;
	}
};

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;
    }
};

//图片切割
var ImgCropper = Class.();
ImgCropper.prototype = {
  //容器对象,控制层,图片地址
  initialize: function(container, handle, url, options) {
	this._Container = $(container);//容器对象
	this._layHandle = $(handle);//控制层
	this.Url = url;//图片地址
	
	this._layBase = this._Container.appendChild(document.Element("img"));//底层
	this._layCropper = this._Container.appendChild(document.Element("img"));//切割层
	this._layCropper.onload = Bind(this, this.SetPos);
	//用来设置大小
	this._tempImg = document.Element("img");
	this._tempImg.onload = Bind(this, this.SetSize);
	
	this.SetOptions(options);
	
	this.Opacity = Math.round(this.options.Opacity);
	this.Color = this.options.Color;
	this.Scale = !!this.options.Scale;
	this.Ratio = Math.max(this.options.Ratio, 0);
	this.Width = Math.round(this.options.Width);
	this.Height = Math.round(this.options.Height);
	
	//设置预览对象
	var oPreview = $(this.options.Preview);//预览对象
	if(oPreview){
		oPreview.style.position = "relative";
		oPreview.style.overflow = "hidden";
		this.viewWidth = Math.round(this.options.viewWidth);
		this.viewHeight = Math.round(this.options.viewHeight);
		//预览图片对象
		this._view = oPreview.appendChild(document.Element("img"));
		this._view.style.position = "absolute";
		this._view.onload = Bind(this, this.SetPreview);
	}
	//设置拖放
	this._drag = new Drag(this._layHandle, { Limit: true, onMove: Bind(this, this.SetPos), Transparent: true });
	//设置缩放
	this.Resize = !!this.options.Resize;
	if(this.Resize){
		var op = this.options, _resize = new Resize(this._layHandle, { Max: true, onResize: Bind(this, this.SetPos) });
		//设置缩放触发对象
		op.RightDown && (_resize.Set(op.RightDown, "right-down"));
		op.LeftDown && (_resize.Set(op.LeftDown, "left-down"));
		op.RightUp && (_resize.Set(op.RightUp, "right-up"));
		op.LeftUp && (_resize.Set(op.LeftUp, "left-up"));
		op.Right && (_resize.Set(op.Right, "right"));
		op.Left && (_resize.Set(op.Left, "left"));
		op.Down && (_resize.Set(op.Down, "down"));
		op.Up && (_resize.Set(op.Up, "up"));
		//最小范围限制
		this.Min = !!this.options.Min;
		this.minWidth = Math.round(this.options.minWidth);
		this.minHeight = Math.round(this.options.minHeight);
		//设置缩放对象
		this._resize = _resize;
	}
	//设置样式
	this._Container.style.position = "relative";
	this._Container.style.overflow = "hidden";
	this._layHandle.style.zIndex = 200;
	this._layCropper.style.zIndex = 100;
	this._layBase.style.position = this._layCropper.style.position = "absolute";
	this._layBase.style.top = this._layBase.style.left = this._layCropper.style.top = this._layCropper.style.left = 0;//对齐
	//初始化设置
	this.Init();
  },
  //设置默认属性
  SetOptions: function(options) {
    this.options = {//默认值
		Opacity:	50,//透明度(0到100)
		Color:		"",//背景色
		Width:		0,//图片高度
		Height:		0,//图片高度
		//缩放触发对象
		Resize:		false,//是否设置缩放
		Right:		"",//右边缩放对象
		Left:		"",//左边缩放对象
		Up:			"",//上边缩放对象
		Down:		"",//下边缩放对象
		RightDown:	"",//右下缩放对象
		LeftDown:	"",//左下缩放对象
		RightUp:	"",//右上缩放对象
		LeftUp:		"",//左上缩放对象
		Min:		false,//是否最小宽高限制(为true时下面min参数有用)
		minWidth:	50,//最小宽度
		minHeight:	50,//最小高度
		Scale:		false,//是否按比例缩放
		Ratio:		0,//缩放比例(宽/高)
		//预览对象设置
		Preview:	"",//预览对象
		viewWidth:	0,//预览宽度
		viewHeight:	0//预览高度
    };
    Extend(this.options, options || {});
  },
  //初始化对象
  Init: function() {
	//设置背景色
	this.Color && (this._Container.style.backgroundColor = this.Color);
	//设置图片
	this._tempImg.src = this._layBase.src = this._layCropper.src = this.Url;
	//设置透明
	if(isIE){
		this._layBase.style.filter = "alpha(opacity:" + this.Opacity + ")";
	} else {
		this._layBase.style.opacity = this.Opacity / 100;
	}
	//设置预览对象
	this._view && (this._view.src = this.Url);
	//设置缩放
	if(this.Resize){
		with(this._resize){
			Scale = this.Scale; Ratio = this.Ratio; Min = this.Min; minWidth = this.minWidth; minHeight = this.minHeight;
		}
	}
  },
  //设置切割样式
  SetPos: function() {
	//ie6渲染bug
	if(isIE6){ with(this._layHandle.style){ zoom = .9; zoom = 1; }; };
	//获取位置参数
	var p = this.GetPos();
	//按拖放对象的参数进行切割
	this._layCropper.style.clip = "rect(" + p.Top + "px " + (p.Left + p.Width) + "px " + (p.Top + p.Height) + "px " + p.Left + "px)";
	//设置预览
	this.SetPreview();
  },
  //设置预览效果
  SetPreview: function() {
	if(this._view){
		//预览显示的宽和高
		var p = this.GetPos(), s = this.GetSize(p.Width, p.Height, this.viewWidth, this.viewHeight), scale = s.Height / p.Height;
		//按比例设置参数
		var pHeight = this._layBase.height * scale, pWidth = this._layBase.width * scale, pTop = p.Top * scale, pLeft = p.Left * scale;
		//设置预览对象
		with(this._view.style){
			//设置样式
			width = pWidth + "px"; height = pHeight + "px"; top = - pTop + "px "; left = - pLeft + "px";
			//切割预览图
			clip = "rect(" + pTop + "px " + (pLeft + s.Width) + "px " + (pTop + s.Height) + "px " + pLeft + "px)";
		}
	}
  },
  //设置图片大小
  SetSize: function() {
	var s = this.GetSize(this._tempImg.width, this._tempImg.height, this.Width, this.Height);
	//设置底图和切割图
	this._layBase.style.width = this._layCropper.style.width = s.Width + "px";
	this._layBase.style.height = this._layCropper.style.height = s.Height + "px";
	//设置拖放范围
	this._drag.mxRight = s.Width; this._drag.mxBottom = s.Height;
	//设置缩放范围
	if(this.Resize){ this._resize.mxRight = s.Width; this._resize.mxBottom = s.Height; }
  },
  //获取当前样式
  GetPos: function() {
	with(this._layHandle){
		return { Top: offsetTop, Left: offsetLeft, Width: offsetWidth, Height: offsetHeight }
	}
  },
  //获取尺寸
  GetSize: function(nowWidth, nowHeight, fixWidth, fixHeight) {
	var iWidth = nowWidth, iHeight = nowHeight, scale = iWidth / iHeight;
	//按比例设置
	if(fixHeight){ iWidth = (iHeight = fixHeight) * scale; }
	if(fixWidth && (!fixHeight || iWidth > fixWidth)){ iHeight = (iWidth = fixWidth) / scale; }
	//返回尺寸对象
	return { Width: iWidth, Height: iHeight }
  }
}