From BlenderWiki
I'm not sure about .kra (krita's file format) but GIMP devs do not encourage supporting .xcf! they reserve it as an internal/native format, not for interchange, I think so they can be free to break compatibility without breaking other applications. On the other hand, there is the format used natively by mypaint, .ora aka open raster, which is a layer supporting, open file format that is targetted as interchange; afaik it is basically compressed .png layers, with some metadata attached for blending modes etc. This format is supported by the major raster graphics oss programs (gimp, krita, mypaint) but I'm not sure it is supported by OIIO also. -Bassam
