function DrawImage(ImgD,iwidth,iheight){
    //参数(图片,允许的宽度,允许的高度)
    var image=new Image();
    image.src=ImgD.src;
    if(image.width>0 && image.height>0){
	    if(image.width/image.height>= iwidth/iheight){
		    if(image.width>iwidth){
				ImgD.width=iwidth;
				ImgD.height=(image.height*iwidth)/image.width;
			}else{
				ImgD.width=image.width;
				ImgD.height=image.height;
			}
        }
		else{
			if(image.height>iheight){
				ImgD.height=iheight;
				ImgD.width=(image.width*iheight)/image.height;
			}else{
				ImgD.width=image.width;
				ImgD.height=image.height;
			}
        }
    }
}