Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!apple!rutgers!mcnc!ecsvax.uncecs.edu!cjl From: cjl@uncecs.edu (Charles J. Lord) Newsgroups: comp.sys.ibm.pc.programmer Subject: Re: 256 GrayScale Matching to 256 Colors Summary: This works! true 256 gray on RGB Keywords: Look Up Table Needed Message-ID: <1990Mar6.190222.14979@uncecs.edu> Date: 6 Mar 90 19:02:22 GMT References: <858@dukempd.phy.duke.edu> <1990Mar2.043848.501@uncecs.edu> <4158@cpoint.UUCP> Organization: Triangle R&D Corp,RTP,NC Lines: 29 In article <4158@cpoint.UUCP>, alien@cpoint.UUCP (Alien Wells) writes: > > It seems to me that a similar thing could be done for a color VGA system. > start with all three colors 0. To fill suceeding registers, use the following > algorithm, cycling until all registers are complete: > - increment R by 1 > - increment G by 1 > - increment B by 1, decrement G by 1 > - increment G by 1 > Thus, you get colors like: > - 00,00,00 01,00,00 01,01,00 01,00,01 01,01,01 02,01,01 > > The nice thing about using this is that the colors rendered would look like > a gray scale (they all approximate the vector running through the center of > color space). The total number of colors is 4 * 2**6 = 2**8 = 256, thus all > registers are used. The only 'bug' is in the one discontinuity where G is > being decremented, but 01,01,00 will at least be different than 01,00,01, > and my suspicion is that the progression would look natural. > I tried it, and it does. There is a slight rainbow effect if you draw a series of vertical lines from 0..255, but in an image it looks very good. A public *thanks*! -- * Charles Lord ..!decvax!mcnc!ecsvax!cjl Usenet (old) * * Cary, NC cjl@ecsvax.UUCP Usenet (new) * * #include cjl@ecsvax.BITNET Bitnet * * #include cjl@ecsvax.uncecs.edu Internet *