//Ëõ·Åº¯Êý
//×÷Õߣº³ÂÁÁÁÁ
function resize_img(mypic,needwidth){ 
   
    var width = mypic.width;  
    var height = mypic.height;        
         
    if(width>needwidth) 
    { 
        var bili = needwidth/width;   
        mypic.width=needwidth; 
        mypic.height=height*bili; 
    } 
    
}