div height 100% with content - html

Question

Would I like to know how I can put in a div 100% height?
I have a div with an image and a div with content.
The image has a width 100%, and the same content but does not fill the entire image div.
I copied the code if you can help.
Thank you,
#carta div{
position: relative;
display: table;
}
#carta div .overlay{
width: 100%;
height: 100%;
background: rgba(0,0,0,.7);
position: absolute;
top:0;
text-align: center;
color:white;
cursor: pointer;
opacity: 0;
-webkit-transition:all .4s ease-out;
transition:all .4s ease-out;
}
#carta .overlay:hover{
opacity: 1;
width: 100%;
height: 100%;
}
#carta .col-1-4{
padding: 0;
margin:0;
}
#carta div img{
width: 100%;
display: table;
}
#carta .overlay p{
font-style: oblique;
font-size: 20px;
padding-top: 50px;
text-align: center;
border-top: 1px solid white;
-webkit-transition:all .4s ease-out;
transition:all .4s ease-out;
}
#carta .overlay h5{
font-size: 30px;
margin: 50px;
}
<div class="clearFix">
<div class="col-1-4">
<img src="img/carta/atun.jpg" alt="atún revuelto"/>
<div class="overlay">
<h5>Atun revuelto</h5>
<p>15€</p>
</div>
</div>
<div class="col-1-4">
<img src="img/carta/especialidaditaliana.jpg" alt="especialidad italiana"/>
<div class="overlay">
<h5>Especialidad Italiana</h5>
<p>15€</p>
</div>
</div>
</div>

Answer 1

Thank you very much for your responses.
I have solved by adding "display: table-cell" in the css class ".overlay"
Thus occupies the div, which occupies the image.
Many thanks

Answer 2

Use background in css,something like this: background: url(img/carta/especialidaditaliana.jpg);
You also can use div to set background
Like this: <div class="img">content</div> but you also need css background.
Something like this?It should work in .html document...
<style>
.img {
position: relative;
width: 200px;
height: 100%;
background: url(http://goo.gl/ytbJn8);
color: white;
}
</style>
<div class="img">This is text. This is text. This is text. This is text. This is text. This is text. This is text. This is text. This is text.</div>
<div class="box"></div>