I use images on a few of my sites for headers to make it look a bit better and its set up like this.

HTML Code:
<h1>
<img src="piclink.jpg" alt="Exactly what the picture says" />
<span style="display:none">Exactly what the picture says</span>
</h1>

So the question is will google still see this text as a heading and can i be penalized for having "hidden" content or am i aloud to do this?

Thank you for any replies.