//图片等比例缩放
function DrawImage(objImg,maxWidth,maxHeight){ 
var img = new Image(); 
img.src = objImg.src; 
var hRatio; 
var wRatio; 
var Ratio = 1; 
var w = img.width; 
var h = img.height; 
wRatio = maxWidth / w; 
hRatio = maxHeight / h; 
if (maxWidth ==0 && maxHeight==0){ 
Ratio = 1; 
}else if (maxWidth==0){ 
if (hRatio<1) Ratio = hRatio; 
}else if (maxHeight==0){ 
if (wRatio<1) Ratio = wRatio; 
}else if (wRatio<1 || hRatio<1){ 
Ratio = (wRatio<=hRatio?wRatio:hRatio); 
} 
if (Ratio<1){ 
w = w * Ratio; 
h = h * Ratio; 
} 
objImg.height = h; 
objImg.width = w;

//if(h<=maxHeight)
//{
//  objImg.style.paddingTop=maxHeight-h;
//}
//if(w<=maxWidth)
//{
//objImg.style.paddingLeft=(maxWidth-w)/2;
//objImg.style.paddingRight=(maxWidth-w)/2;
//}
}
//<img onload="DrawImage(this,140,120)" src="ss.jpg"/>