text: 	 var allowExt = ['jpg', 'gif', 'bmp', 'png', 'jpeg'];
  	 var preivew = function(file, container){
  		 try{
  			var pic =  new Picture(file, container);
  		 }catch(e){
  			 alert(e);
  		 }
  	 }
  	 //缩略图类定义
       var Picture  = function(file, container){
  		 var height	= 0, 
  			 widht 	= 0, 
  			 ext	= '',
  			 size	= 0,
  			 name   = '',
  			 path  	=  '';
  		 var self 	= this;
  		 if(file){ 
  		     name = file.value;
  			 if (window.navigator.userAgent.indexOf("MSIE")>=1){ 
  				 file.select(); 
  				 path = document.selection.createRange().text; 
  			 }else if(window.navigator.userAgent.indexOf("Firefox")>=1){ 
  				 if(file.files){ 
  					 path =  file.files.item(0).getAsDataURL(); 
  				 }else{
  					 path = file.value;
  				 }
  			 } 
  		 }else{
  			 throw "bad file";
  		 } 
  
  
  		 ext = name.substr(name.lastIndexOf("."), name.length);
  
  		 if(container.tagName.toLowerCase() != 'img'){
  			 throw "container is not a valid img label";
  			 container.visibility = 'hidden';
  		 }
  		 container.src = path;
  		 container.alt = name;
  		 container.style.visibility = 'visible';
  		 height = container.height;
  		 widht  = container.widht;
  		 size   = container.fileSize;
  
  
  		 this.get = function(name){
  			 return self[name];
  		 }
  
  		 this.isValid = function(){
  			 if(allowExt.indexOf(self.ext) !== -1){
  				 throw 'the ext is not allowed to upload';
  				 return false;
  			 }
  		 }
  	 }