I have used SlideshowPro Director, along with it's PHP API, as an Image Management System on several sites in the past. The backend is incredibly well-designed and easy to use, and the system stores original quality uploads, so you can request specific images sizes and have them dynamically created without much trouble.
However, it seems that SlideshowPro Director, especially the API, is not receiving as much attention from the developer as it used to, and I am tired of running into problems with no solutions.
Is anyone aware of any PHP-based Image/Portfolio Management Systems that have similar capabilities and are similarly well-designed? Open-source or commercial are both fine.