I'm wondering whether PPM support is planned for Seashore? I'd be happy to help add it (as long as it can be done in C or C++).
I tend to use PPM a lot for silly little image generation programs but I don't want to put up with GIMP any more :) Thanks /so/ much for taking the time to scratch that itch, by the way!!!
Seashore supports XBM, so I guess there is no reason it should not support PPM.
I am not planning to implment it though, so please feel free to play around with Seashore yourself and send me the patch.
The majority of stuff you do will be C-based though there will be a small bit of Objective-C. You will need to use XCode.
You will need to write files similar to "source/document/XBMContent.m", "source/document/XBMLayer.m" and "source/document/PNGExporter.m" and call them "PPMContent.m", "PPMLayer.m" and "PPMExporter.m". You will also need to edit Seashore's target (the "Properties" pane) in XCode and the "readFromFile:ofType:" and "writeToFile:ofType:" of "SeaDocument.m" to hook your new file format into the program. External libraries can probably be used but may be dropped if they are too big (I don't want an extra 100 kB added on to Seashore to support PPM).
I can easily make an icon for you if you do implement it though.
If you have any more questions you are welcome to submit them to our developer's mailing list:
Hope this helps,
I'll try and find some time to have a stab at it soon.