Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!sdd.hp.com!hplabs!hpda!hpcuhb!hpcuhe!edwardm From: edwardm@hpcuhe.cup.hp.com (Edward McClanahan) Newsgroups: comp.sys.next Subject: Re: Colour Palette on a ColorStation Message-ID: <32370001@hpcuhe.cup.hp.com> Date: 18 Apr 91 00:00:47 GMT References: Organization: Hewlett Packard, Cupertino Lines: 40 Sam Streeper explains: > ----- Begin wayward color lookup table discussion -------------- > > By the way, NeXTstation hardware does NOT utilize color lookup tables. > In other words, every pixel has a specified color rather than an index > into a table that specifies the color. > > If a system has 256 colors onscreen from a pallette of 4096, that means > every pixel has 8 bits specifying an index into a color table > with 256 entries, each of which is a 12 bit color specification. Color > lookup tables have a few keen features, but they can also be a big pain > in the rear. This may be misleading, however. Just because a system can display all 4096 possible colors on the screen at the same time (from a "pallette" of 4096 colors) does not mean it LACKS a Color Lookup Table. One justification for a CLT pointed out several months ago that it can be used to tweak the mapping (away from 1-to-1) to allow for deficiencies in the D->A converter and the relative strengths of the RGB guns (as well as the surrounding lighting). Also, it is possible to modify entries in the CLT during the page update cycle (i.e. as the display hardware is reading the pixel "values" from memory, using these "values" to index into the CLT to find the Digital RGB values to convert to Analog values to send to the RDB guns in the monitor). Obviously, this method must be applied every screen refresh (30-?? times per second). So, I still have not heard a definitive statement as to the lack or existence of a CLT on the NeXT (4-bit mono, 12-bit color, or 24-bit color). Does anybody know for sure? =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Edward McClanahan Hewlett Packard Company -or- edwardm@cup.hp.com Mail Stop 42UN 11000 Wolfe Road Phone: (480)447-5651 Cupertino, CA 95014 Fax: (408)447-5039