This sound like hard but some companies seems to make it work. Xee can read PSD too (and has an epic comment about this format in the source code).
But to quote someone over at HN:
PSD was never intended to be a data interchange format: it is the serialization format of a single program that has more individual unrelated features that actual people rely on than almost any other piece of software and has maintained striking amounts of backwards compatibility and almost unbroken forwards compatibility during its over two decades of existence. This product's "file format" needs to be critiqued in this context, along with similar mega-programs like Office. I am thereby having a difficult time fathoming why anyone would think that a PSD file is thereby going to be some well-organized file format that they should easily be able to parse from their own application is just naively wishful thinking: even other products from Adobe have limitations while opening these files; to truly manipulate these files you really need to be highly-compatible with Photoshop's particular editing model (hence the conceptual difference between these two classes of file format).
I would recommand to look at Xee for a server side utility.
Good luck.