上传图片在客户端用Javascript做图片检验，并显示图片缩略图

         function  PreviewImage(x)
        {
            
             // var x = document.getElementById('File1');
             var  xid = x.id + "" ;
             var  index = xid.substr(xid.length - 1 , 1 );
            
             if ( ! x  ||   ! x.value) 
                {                         
                 return   false ;
                }
             var  patn  =   / \.jpg$|\.jpeg$|\.bmp$|\.gif$ / i;
             try
            {
                 var  obj  =  document.getElementById( ' PhotoPreviewImg ' + index);
                
                 var  barType = index;
                 // 默认普通标题图
                 var  width = 120 ;
                 var  height = 80 ;
                
                 if  (barType == 2 )  // 首页标题图
                {
                    width = 120 ;
                    height = 90 ;
                }
                 else   if  (barType == 3 )  // 焦点图
                {
                    width = 320 ;
                    height = 240 ;
                }
                 if (patn.test(x.value))
                    {
                     var  prvImg  =   " <img src='file://localhost/ "   +  x.value  +   " ' style='width:  " +  width  + " px; height:  " +  height  + " px; border: 1;' /> " ;                    
                     var  prvImgsrc  =   ' file://localhost/ '   +  x.value;
                    document.getElementById( " PhotoPreviewImg " + index).innerHTML = prvImg;
                     // setTimeout('CheckImg()',300);
                     // imgwh = new Image();
                     // imgwh.src = "file://localhost/" + x.value;
                     // CheckImg();
                    } 
                 else
                    {                    
                    alert( " 您选择的似乎不是图像文件 " );
                     return   false ;
                    }
            
            }
             catch (e)
            {
             alert( " 您选择文件无法预览，或网络故障无法上传，请稍候再试！ " );
              return   false ;
            }
        }
        
    
         
 
    
         function  CheckImg()
        {
             if (document.getElementById( " PhotoPreviewImg " ).fileSize ==- 1 || document.getElementById( " PhotoPreviewImg " ).fileSize > 5000000 )
                        {
                             document.getElementById( " File1 " ).disabled = false ;
                              // document.getElementById("PhotoPreviewImg").className='imgPrev0';
                             document.getElementById( " PhotoPreviewImg " ).src = "" ;
                             LoadEmptyImage ();
                             alert( " 您选择文件超过5M，无法上传！ " );

                              return   false ;                                
                        }
             else
            {
                document.getElementById( " File1 " ).disabled = false ;
            }
                    
                document.getElementById( " PhotoPreviewImg " ).className = '' ;
                 var  originwidth = document.getElementById( " PhotoPreviewImg " ).width * 10 ;
                 var  originheight = document.getElementById( " PhotoPreviewImg " ).height * 10 ;
                 var  scale = originwidth / originheight;                        
                document.getElementById( " PhotoPreviewImg " ).style.top = 20 ;
                document.getElementById( " PhotoPreviewImg " ).style.left = 20 ;
                
                 if (scale > 0.8 )
                    {
                    document.getElementById( " PhotoPreviewImg " ).className = ' imgPrev2 ' ;
                     var  largerheight = document.getElementById( " PhotoPreviewImg " ).height;
                     var  leftover = ( 150 - largerheight) / 2;
                    document.getElementById( " PhotoPreviewImg " ).style.marginLeft = 2 ;                
                    document.getElementById( " PhotoPreviewImg " ).style.marginTop = leftover;
                    }
                 else
                    {                                                            
                    document.getElementById( " PhotoPreviewImg " ).style.marginTop = 2 ;
                    document.getElementById( " PhotoPreviewImg " ).className = ' imgPrev1 ' ;
                     var  largerwidth = document.getElementById( " PhotoPreviewImg " ).width;
                     var  leftover = ( 120 - largerwidth) / 2;                        
                    document.getElementById( " PhotoPreviewImg " ).style.marginLeft = leftover;
                    }                                                

                     return   true ;
    
        }

 

     < script type = " text/javascript "  defer >
             function  checkit(obj)
            {
                 if  (obj.value.length  >=   16 )
                {
                    alert( " 在这里输入照片标题，不超过16个字！ " );
                     var  str  =  obj.value;
                    obj.value  =  str.substring( 0 , 16 );
                     return   false ;
                }
                 return   true ;
            }
             function  empty()
            {
                 if (document.getElementById( " <%= phDescription1.ClientID%> " ).value  ==   ""   ||  document.getElementById( " <%= phDescription1.ClientID%> " ).value  ==   " 在这里输入照片标题，不超过16个字 " )
                {
                    document.getElementById( " <%= phDescription1.ClientID%> " ).value  =   "" ;
                }
            }
             function  noempty()
            {
                 if (document.getElementById( " <%= phDescription1.ClientID%> " ).value  ==   "" )
                {
                    document.getElementById( " <%= phDescription1.ClientID%> " ).value  =   " 在这里输入照片标题，不超过16个字 " ;
                }
            }
            
             var  imgwh;

             function  PreviewImage1()
            {
                 var  x  =  document.getElementById( ' <% = UpImg1.ClientID %> ' );
                 if (x  !=   null )
                {
                    checkupfile(x);
                }
            }
            
             function  checkupfile(x)
            {
                 if ( ! x  ||   ! x.value) 
                {                         
                     return   false ;
                }
                 var  patn  =   / \.jpg$|\.jpeg$|\.bmp$|\.gif$ / i;
                 try
                {
                     if ( ! patn.test(x.value))
                    {            
                        alert( " 您选择的图片格式不正确，请选择jpg，jepg，gif，bmp格式的图片！ " );
                         return   false ;
                    }
                     else
                    {
                        imgwh  =   new  Image();
                        imgwh.src  =  x.value;
                    }
                }
                 catch (e)
                {
                     // alert("您选择文件无法预览，或网络故障无法上传，请稍候再试！");
                     return   false ;
                }
            }

             function  BeforeSaveClick()
            {
                 var  x  =  document.getElementById( " <% = UpImg1.ClientID %> " );

                 if ( ! x  ||   ! x.value) 
                { 
                    document.getElementById( ' <%= Span1.ClientID%> ' ).innerHTML  =   " 请选择要上传的照片。 " ;
                     return   false ;
                }
                 var  patn  =   / \.jpg$|\.jpeg$|\.bmp$|\.gif$ / i;
                 try
                {
                     if ( ! patn.test(x.value))
                    {            
                        alert( " 您选择的图片格式不正确，请选择jpg，jepg，gif，bmp格式的图片！ " );
                         return   false ;
                    }
                     else
                    {
                                                
                         var  sz  =  imgwh.width  +   " x "   +  imgwh.height;
                        document.getElementById( " hidImageWH " ).value  =  sz;
                        
                        document.getElementById( " hidImageWH_url " ).value  =  x.value;
                         return   true ;
                    }
                }
                 catch (e)
                {
                    alert( " 网络故障无法上传，请稍候再试！ " );
                     return   false ;
                }
            }

             < / script>