function popup(dochtml, altura, largura) {
 windowTop = screen.height/2 - altura/2;
 windowLeft = screen.width/2 - largura/2;

window.open('midia.detalhes.php?imagem='+ dochtml +'','_blank','scrollbars=yes,toolbar=no,location=no,directories=no,status=no,menubar=no,resizable=no,copyhistory=no,height='+ altura +',width='+ largura +',top='+ windowTop +',left='+ windowLeft +''); 

}