写了一个图片预览程序,抄多写少,理解为重

   

<script language="javascript" type="text/javascript">
    //==============================
    //功能:Javascript本地图片预览
    //Author:orichisonic
    //Site:http://blog.youkuaiyun.com/orichisonic
    //Date:2006-07-26
    //说明:简单的判断了文件的合法性
    //适用于:上传文件前预览本地图片
    //==============================
     function ShowImage(value,img)
    ...{
            //alert(value);
            //检测盘符
            //alert(value.indexOf(':'));
            //检测文件是否有扩展名
            //alert(value.length-value.lastIndexOf('.'));
            //取文件扩展名
            //alert(value.substr(value.length-3,3));
            //检测文件扩展名是否合法
            //alert(CheckExt(value.substr(value.length-3,3)));
            
        if(value.length>5&&value.indexOf(':')==1&&(value.length-value.lastIndexOf('.'))==4&&CheckExt(value.substr(value.length-3,3)))
        ...{
            img.src=value;
            img.alt="本地图片预览";
            img.style.visibility="visible";
        }
        else
        ...{
                    img.style.visibility="hidden";
              }
    }
    //检查扩展名是否合法,合法返回True
    function CheckExt(ext)
    ...{
        //这里设置允许的扩展名
        var AllowExt="jpg|gif|jpeg|png|bmp";
        var ExtOK=false;
            var ArrayExt;
            if(AllowExt.indexOf('|')!=-1)
            ...{
                ArrayExt=AllowExt.split('|');
                for(i=0;i<ArrayExt.length;i++)
                ...{
                    if(ext.toLowerCase()==ArrayExt[i])
                    ...{
                        ExtOK=true;
                        break;
                    }
                }
            }
            else
            ...{
                ArrayExt=AllowExt;
                if(ext.toLowerCase()==ArrayExt)
                ...{
                    ExtOK=true;
                }
            }
            return ExtOK;
    }
</script>

在aspx中加入asp控件

<asp:Image id="Image1" style="visbility:hidden" runat="server" ></asp:Image>

 

问题解决了,发觉如果和缩略以及水印功能联动,效果也许更好.