hi Iohannes,
i made a pull request directly on github did you received it ? I think not... because I clone the sourceforge repos and push it on a new github repo it could have worked if I'd made a fork instead of a clone, isn't it ? is there any way to do a fork from sourceforge repos ?
anyhow, I wrote some lines of code to add relative path support to pix_write those are in the branch pix_write of my github repos : https://github.com/avilleret/Gem
i don't know if this code is in the right Gem coding style but it was a good opportunity for me to put my hands deep in the code...
cheers
antoine