function maxSize(obj,w,h){
    if(obj.readyState != "complete") return "auto";
    real_w=obj.offsetWidth;
    real_h=obj.offsetHeight;
    virt_w=obj.offsetWidth;
    virt_h=obj.offsetHeight;
    if(w>0 && virt_w>w){
        virt_w = w;
        virt_h = real_h * (virt_w/real_w);
    }
    if(h>0 && virt_h>h){
        virt_h = h;
        virt_w = real_w * (virt_h/real_h);
    }

    obj.style.width="0";
    obj.style.height="0";
    obj.style.width=virt_w+"px";
    obj.style.height=virt_h+"px";

}