Make and edit .psd file in iPhone file system

Writing a psd parser yourself is a futile business. See the super-famous quote from here (original source code)

            // At this point, I'd like to take a moment to speak to you about the Adobe PSD format.
            // PSD is not a good format. PSD is not even a bad format. Calling it such would be an
            // insult to other bad formats, such as PCX or JPEG. No, PSD is an abysmal format. Having
            // worked on this code for several weeks now, my hate for PSD has grown to a raging fire
            // that burns with the fierce passion of a million suns.

It goes on and on. So, look for an (open-source) psd reading/writing library.

I'm the author of the Layers app the OP mentioned. Unfortunately, coneybeare is right - I pretty much wrote an objective-c implementation from scratch. The trick turned out to be basing it off a very old version of the PSD spec, from before it got insanely polluted with crap. Layers actually writes Photoshop 3 files.

UPDATE: I've published the PSDWriter from Layers on github. You can use it to write PSD files from a set of UIImages on iOS or Mac OS X: https://github.com/bengotow/PSDWriter

Enjoy!

Checkout ImageMagick. There's an iOS compiled binary that you can link into your application. Or if you want, you can set up the compilation business yourself.