Optional dependencies are:
- libraw, libtiff, libjpeg, libpng for RAW, TIFF, JPE, PNG and images import and export. The libraries are detected at compilation-time.
- FFMS2 for film native support as image sequences. It also allows frames to be extracted from many kinds of film, for other purposes than astronomy. Versions < 2.20 have an annoying bug. It is recommanded to install the last version.