图片加载并按比例缩小到合适大小（非原创）

// 图片加载并按比例缩小到合适大小
// <img src=""  width="80" onload="DownImage(this,80,0,0);">
function DownImageWidth(ImgD,MaxWidth,alignX,alignY)
{
    alignX = alignX || 1 ;
    alignY = alignY || 1 ;
    var image = new Image();
    image.src = ImgD.src;
    if (image.width > 0 && image.height > 0 )
    {
        var rate = MaxWidth / image.width;
        var wid = 0 ;
        var hid = 0 ;
        if (rate <= 1 )
        {
            wid = ImgD.width = image.width * rate;
            hid = ImgD.height = image.height * rate;
        }
        else
        {
            wid = ImgD.width = image.width;
            hid = ImgD.height = image.height;
        }
    }
}