Custom code for images on a page

[dedos]

Hello.
I'm finishing my first GetSimple template for my new website.
I wish that all images that appear inside my page content will be encoded like this:

Code:

<figure>
<img src="img/outono2013.jpg" alt="two paintings by rafael" />
<figcaption><span>pinturas outono 2013</span></figcaption>
</figure>

So basically it would be adding the

Code:

figure

element around the image along with a caption. The automated code generated by getsimple generates the

Code:

img

tag alone.

I can do this myself alone while i'm writing posts, but i pretend to use this for a client so i wonder if this can be automated.
Thanks and I'm loving GetSimple so far.