function otvor_obr_okno(img)
{ 	
    obr_subor = new Image(); 
    obr_subor.src =(img); 

    if( (obr_subor.width != 0) && (obr_subor.height != 0) )
    { 
	    ht = obr_subor.height + 20;
    	wd = obr_subor.width + 20; 

	    var args= "height=" + ht + ",innerHeight=" + ht;
    	args += ",width=" + wd + ",innerWidth=" + wd;
    	if (window.screen) 
    	{ 
        	var avht = screen.availHeight; 
        	var avwd = screen.availWidth;
        	var xcen = (avwd - wd) / 2; 
        	var ycen = (avht - ht) / 2;
        	args += ",left=" + xcen + ",screenX=" + xcen;
        	args += ",top=" + ycen + ",screenY=" + ycen + ",resizable=yes"; 	
    	}
    	window.open(img, '', args); 
    }
}