Hallo Matthias,
By default we have separate processes per user connection which means one core per user session. For hot-folder batch image conversion we use MAX-CPUs as the default to use the number of available core but not to overload the system. For WebShare gallery preview rendering multiple images are getting rendered in parallel. All this should be fine so far.
Our sample-images conversion script uses only one-core as this is to demos how to use our cmd line image conversion args.
For image rendering (PDFs, JPEG200, TIFF, etc.) we use only one core per conversion. Yes there is room for enhancement, however it is not always so easy because a PDF must basically be interpreted sequential PDF stream to have the correct drawing order so there is little root for multi-cpu work. For images the biggest bottleneck area are scaling and ICC color transformations, yes multi-core can help here to get it faster, a GPU mould be even better because for this stupid tasks it would be qualified best. Yes there is room for improvements.
