xref: /xsrc/external/mit/rgb/dist/others/README

This directory contains several alternative rgb databases:

    old-rgb.txt			the version that was shipped in previous 
				releases; this was originally "tuned" for
				the Digital VT240 series terminals.

    raveling.txt		lots of new colors, tuned by Paul Raveling
				at ISI for the HP monitor; see below.

    thomas.txt			a version of the older database that was 
				tuned by John Thomas at Tektronix to match
				a box of Crayola crayons; see below.


Notes from Paul Raveling:

        1.  Many colors have been tuned for an HP monitor -- mine,
            to be exact.  Some of the old values were obnoxious enough
            to bring complaints from users (like "That's Wheat???!!!");
            so far early user reports on the new RGB database are favorable.

        2.  File rgb.txt was reorganized into 3 sections:

            a)  Light and off-white colors, copied from several Sinclair
                Paints color samples.  The intent for adding these is
                to provide a better choice for light-colored window
                backgrounds.

                BTW, I wanted to find ANSI standard colors, but ANSI
                happily gobbled my $16 without sending the specification
                I ordered,  Then they ignored my followup letter.
                Nuts to ANSI & "ANSI standards".

            b)  Special colors such as black, white, and favorite
                shades of gray.

            c)  A spectrum of colors, arranged to transition gradually
                between nearby colors, running from generally blue
                colors through green and ending with generally red colors.
                This includes all colors from the old X11R3 database,
                but they're no longer in (mostly) alphabetic order.

            d)  The gray scale from the original X11R3 database.


        Within the "spectrum of colors" section there are clusters
        of colors, each consisting of:

            1.  One or more Specially named colors.  If more than one
                is present, all are related by lying on a common line
                running from RGB = (0 0 0) [pure black] to a single
                point on the surface of the RGB color cube.

            2.  Four colors at particular points on the same line in
                RGB space.  Their names end in "1", "2", "3", and "4",
                with "color1" being at the surface of the color cube
                and the others at increasing distances approaching black.
                Distance of these color points from black is approximately
                logarithmic.  This attempts a rough fit to human
                perception's sensitivity to intensity.

        Here's an example of one of these clusters:

                210 105  30             chocolate
                139  69  19             saddle brown
                139  69  19             SaddleBrown
                255 127  36             Chocolate1
                238 118  33             Chocolate2
                205 102  29             Chocolate3
                139  69  19             Chocolate4

        Note that the "original" colors, in this case chocolate
        and saddle brown, don't always match the scaled points.


        Does anyone think these changes are a good idea?  Crummy idea?
        Do you have other favorite colors?   Can anyone do better at
        matching some tough colors?  Some colors, especially reddish
        ones, were VERY hard to reproduce, & I'd welcome contributions
        from other HP users who can get a better match.



Notes from John Thomas:

Advised by our human factors folks that "standard" named colors exist, but
only for well-controlled color coordinate systems (like CIE, but not for RGB),
I sat down one evening with the handiest standard of subjective color names,
a box of 72 Crayola crayons.  (Believe it or not, over 50% of the colors from
rgb.txt were represented.)

Using an X-client implementation of the TekColor model, I created the following
list of named colors.  Appearance on your monitor may vary because of brand,
age, and video drive circuitry, but I think you will find it a better match
for the average monitor, than the original rgb.txt file from MIT.


 John C Thomas
 Tektronix, Inc.
 Wilsonville, OR
 jct@windex.TEK.COM