Hugin (media-gfx/hugin) for panorama stitching. See the above image (and in particular click on it for a better view!) for one of the amazing results. The file is not really perfect yet and probably will never be, as boats tend to move with the waves. Even after removing all useless alignment points and adding many correct ones manually, if you look very closely there are some shifts. Nevertheless, I think the result is pretty neat. The image is assembled from 16 separate free-hand portrait photographs, each with resolution 3456 x 2304; after cropping the total size of the assembled image is 20227 x 1390.