I'm finding the learning curve to the methods in php steep and since I'm on a deadline though maybe I would ask for a bit of help. In nip2 there is Toolkit -> Filter -> Blend -> Blend Alpha, which works well for my purpose as it allows overlay mode, opacity, and offset. But I can't seem to replicate this in PHP.

Also, I know it's probably super straightforward but I also can't seem to do a photographic negative filter in PHP, I thought maybe maplut() could do it?