function PreviewPic(pic_path, dim_x, dim_y) {
        var winl = (screen.width - dim_x) / 2;
        var wint = (screen.height - dim_y) / 2;
	window.open(pic_path,'preview_pic','resizable=yes,scrollbars=yes,width='+dim_x+',height='+dim_y+',top='+wint+',left='+winl);
}