Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Linux advocates are familiar with the refrain that would-be switchers in the graphic arts have to rely on Adobe Photoshop under Windows because it can do things that the GIMP can't. An important but altogether different hurdle is the installed (and paid-for) base of often expensive third-party Photoshop plugins. But a solution to that problem might be easier than you think.
The key is a piece of software called pspi (for Photoshop Plugin Interface), written by GIMP hacker Tor Lillqvist. It is a GIMP plugin that acts as a bridge between the GIMP and Photoshop plugins; to the Photoshop plugin it looks like a full, running copy of Photoshop. It provides the hooks into the menus and functions of Photoshop that the plugin expects to see, and connects them to the GIMP's extension and menu system.
This software bridge is only possible because Adobe makes a Photoshop Software Development Kit to encourage third-party developers to write plugins, and because most of those plugins are self-contained. In particular, most draw their own user interfaces instead of calling on the native Windows and Mac toolkits. It allows them to be cross-platform, an important cost-saver in the Mac-heavy graphics field.
The downside (as you might expect) is that many of these in-house-developed UIs are garish, quirky eyesores that violate accepted standards of usability. But that is something you have to live with if you want to make use of some of the latest Photoshop plugins.