<img src="../img/012.jpg" class="img-responsive center-block" alt="titulo"/>

<div class="col-md-6 .img-responsive center-block">
  <img src="../img/012.jpg" class="img-responsive" alt="titulo"/>
  <div class="h-30"></div>
</div>

<div class="col-md-6 text-center">
  <img src="../img/012.jpg" class="img-responsive" alt="titulo"/>
  <div class="h-30"></div>
</div>

<div class="col-md-6 ">
    <img src="../img/012.jpg" class="img-responsive" alt="titulo"/>
    <div class="h-30"></div>
</div>

img.img-responsive {
    margin: auto
    display: block
}

<div class="col-md-6 ">
  <img src="../img/012.jpg" class="img-responsive" style="display:inline" alt="titulo" />
  <div class="h-30"></div>
</div>