function zoomImg(myPic,myWidth,myHeight){
	var srcWidth = myPic.width;
	var srcHeight = myPic.height;
	if(srcWidth>myWidth || srcHeight>myHeight){                 
		var rateWidth = myWidth/srcWidth; 
		var rateHeight = myHeight/srcHeight;      
		var rate;
		if(rateWidth < rateHeight) {
			rate = rateWidth;
		}else{
			rate = rateHeight;
		}
		myPic.width	 = srcWidth * rate;
		myPic.height = srcHeight * rate;
	}
	$(myPic).css("margin-left",(myWidth-myPic.width)/2+"px");
	$(myPic).css("margin-top",(myHeight-myPic.height)/2+"px");
}