clacImgZoomParam方法源码

function clacImgZoomParam( maxWidth, maxHeight, width, height ){  //传入四个参数：最大宽度，最大高度，宽度，高度；
    var param = { width, height:height, top:0, left:0 };  
  
    if( width>maxWidth || height>maxHeight ){  
        rateWidth = width / maxWidth;  
        rateHeight = height / maxHeight;  
  
        if( rateWidth > rateHeight ){  
            param.width = maxWidth;  
            param.height = height / rateWidth;  
        }else{  
            param.width = width / rateHeight;  
            param.height = maxHeight;  
        }  
    }  
  
    param.left = (maxWidth - param.width) / 2;  
    param.top = (maxHeight - param.height) / 2;  
  
    return param;  
}
通过这个方法可以很好的判断图片的大小，并以适合的宽高显示在页面中