javascript控制图片等比例缩放

<SCRIPT language="JavaScript">
function DrawImage(ImgD,FitWidth,FitHeight){
    var image=new Image();
    image.src=ImgD.src;
    if(image.width> && image.height>){
        if(image.width/image.height>= FitWidth/FitHeight){
            if(image.width>FitWidth){
                ImgD.width=FitWidth;
                ImgD.height=(image.height*FitWidth)/image.width;
            }
            else{
                ImgD.width=image.width;
                ImgD.height=image.height;
            }
        }
        else{
            if(image.height>FitHeight){
                ImgD.height=FitHeight;
                ImgD.width=(image.width*FitHeight)/image.height;
            }
            else{
                ImgD.width=image.width;
                ImgD.height=image.height;
            }
        }
    }
}  

</script>