Graphos is the vector-drawing application for GNUstep (and MacOS) of the GNUstep Application Project.
While it is centered on drawing bezier paths and derived shapes, I added support for copy&pasting images. While these images cannot be saved (the format doesn't support it yet) they still can be useful: since they are layered as any other object (and transparency alpha channel is honoured too), one can do interesting things as in this example:
We paste in the original image for LaternaMagica's icon. We start tracing it with simple shapes, here shown in black.
One can easily fit curves over the image, essentially doing a hand-trace. Very important is the usage of cusps and symmetric handles in bezier-paths, which will be the new feature of the upcoming Graphos release.
After a quick work, this is the first rough result:
I still need to fix some details: the display at zoom rates different than 100% doesn't work correctly with images.