How to add custom image tag to pagedown?

I'm attempting to duplicate the original img tag's functionality in custom img tag that will be added to the pagedown converter.

e.g I'm copy the original behavior:

![image_url][1] [1]: http://lolink.com gives <img src="http://lolink.com">

into a custom one:

?[image_url][1] [1]: http://lolink.com gives <img class="lol" src="http://lolink.com">

Looking at the docs the only way to do this is through using the preblockgamut hook and then adding another "block level structure." I attempted doing this and got an Uncaught Error: Recursive call to converter.makeHtml

here's the code of me messing around with it:

    converter.hooks.chain("preBlockGamut", function (text, dosomething) {
        return text.replace(/(\?\[(.*?)\][ ]?(?:\n[ ]*)?\[(.*?)\])()()()()/g, function (whole, inner) {
            return "<img src=" + dosomething(inner) + ">";
        });
    });

I'm not very experienced with hooks and everything so what would I do to fix it? Thanks.

UPDATE: found out that _DoImages runs after prespangamut, will use that instead of preblockgamut