RE: Color names and the 10 elementary colors?
- To: mathgroup at smc.vnet.net
- Subject: [mg67598] RE: [mg67528] Color names and the 10 elementary colors?
- From: "David Park" <djmp at earthlink.net>
- Date: Sat, 1 Jul 2006 05:13:01 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
First, if you use DrawGraphics, the DrawGraphics palette has all the named
colors on it - displayed as colors. The colors are grouped roughly in six
color bands so all the greenish colors, for example, are grouped together.
When you click on a color it pastes the color name in your notebook. They
are not converted to RGBColor until they are evaluated.
It was in Version 5.1 that WRI moved some of the named colors to the kernel
from the Graphics`Colors` package. I suppose the reason was that users
wouldn't have to load a package to get the most common color names.
Nevertheless, I think this was a serious mistake because it broke the
uniform treatment of the named colors. If you check the MathGroup postings
back then you will see that I complained vociferously about it.
The uniformity of the named colors was also broken in another more serious
way. The neutral colors, Black, White and Gray were changed from an RGBColor
representation to a GrayLevel representation. This not only broke user code,
but even broke WRI's own code. For example, the Raster function, which
underlies DensityPlots, requires that all the colors have the same
representation. So, as an example, the following code gives errors and
incorrect colors.
Needs["Graphics`Colors`"]
myArray = N[Table[Sin[x y], {x, 1, 40}, {y, 1, 40}]];
colorfun[z_] :=
Which[
z < -0.75, Gray,
z < -0.5, LightCoral,
z < 0.0, PaleGreen,
z < 0.5, CadetBlue,
z < 0.8, GeraniumLake,
True, UltramarineViolet
]
ListDensityPlot[myArray, Mesh -> False, ColorFunction -> colorfun,
ColorFunctionScaling -> False];
(There is also another error if you try to convert the above plot to
Graphics format. This produces a Raster array as a primitive, but they
forgot to copy the ColorFunctionScaling option into the Raster statement. It
is a proper and necessary option for Raster as is ColorFunction, which they
do copy in.)
There is another slight error, in my view, in the named colors in that
SeaGreen and DarkSeaGreen seem to be reversed. DarkSeaGreen appears to my
eyes to be lighter than SeaGreen.
When I asked what reason WRI had for breaking the uniform treatment of the
named colors they replied 'efficiency'. However, it is certainly not more
efficient if one has to check for and handle special cases. I would still
like to see the treatment for the named colors restored to the pre Version
5.1 state.
David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/
From: AES [mailto:siegman at stanford.edu]
To: mathgroup at smc.vnet.net
When I recently inquired about using the names of Mathematica colors
("CinnabarGreen", etc.) as label strings in a series of test plots,
several responses proposed that I needed to manually input the names in
quotes. Brian Higgins suggested, however, a terse but somewhat arcane
way to get color names as strings together with the corresponding RGB
values with the Input line
allColorNames =
({#1, ToColor[ ToExpression[#1], RGBColor]}&) /@ AllColors;
so that the Input
allColorNames[[4]]
produces the Output
{ Apricot, RGBColor[1., 0.340007, 0.129994] }
(although his Output showed quotes around "Apricot" and mine doesn't.)
Since my objective was to test all varieties of Green, I added to this a
more crudely programmed statement to generate a list of all the green
color names and color values, viz.
allGreens={ };
Do[
If[ StringMatchQ[ allColorNames[[k,1]], "*Green*" ],
AppendTo[ allGreens, allColorNames[[k]] ] ],
{k, 1, Length[ allColorNames ]} ];
This works fine -- until you notice that just plain "Green" itself is
not in the resulting list. In fact, Green (along with Red, Blue, Brown,
Orange, and 4 or 5 other "elementary colors") is not in AllColors.
I believe in earlier versions of Mathematica one had to use Graphics`Colors`
to
access even these elementary colors, and so they were presumably once
included in AllColors (?); and I think I've learned somewhere that 10 or
so of these elementary colors are now included within "plain
Mathematica" and no long require calling the Graphics`Colors` package.
But:
1) I'd sure like to understand the logic of not continuing to use these
colors in AllColors nonetheless. Removing them seems a confusing and
less than helpful choice to me at any rate. And,
2) Where -- or more important, how -- can the nonexpert user get at the
list of these elementary colors?
As a challenge, try invoking online Help on "Color" or "Colors" or any
one of the elementary color names, and see if, using no more than 5
subsequent mouse clicks within the Help screen, no typing, and no
pre-existing expert knowledge, just "common sense", you can find your
way to the list of those colors.