These drivers are currently not in the official distrib. The support for the hp670, hp690, hp890 and hp1600 was added by Martin Gerbershagen. See the GNU General Public License for more details. Resolved all but one of the known bugs, introduced a couple of perfomance improvements. Martin has also resolved all known bugs.
Dark colors are still pale.
The hp690 is supported through the hp670 device, the hp855, hp870 and the hp1100 through the hp850 device. To use gamma in the traditional way, set MasterGamma to any value greater 1.0 and less 10.0. With the next release, gamma functions will be dropped. Maybe I can optimize the code for text-only pages in a later release. This will only work, when -dMasterGamma is set to a value greater than 1.0.