Verfassergeist

I wanted to do something like this:

Hi there. I've been creeping on the forum for a couple of days now, and I think I have a question. I wanted to take a photo, say, of a generic fish, and then fit the text to outline, making the fish out of text, and not just overlaying the text. Does anybody know where I could find a tutorial that could point me in the right direction? Or maybe some tips or an idea as to how to go about it?