#170: r.colors: make nice random colors like r.watershed
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Reporter: hamish | Owner: grass-dev at lists.osgeo.org
Type: enhancement | Status: new
Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Resolution: | Keywords: r.colors
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Comment (by hamish):
Replying to [comment:2 glynn]:
> If I'm reading the code correctly, it creates a set of random
> colours, then replaces any dark colours with non-random colours
> selected from generated gradients. IOW, it's a fudge which
> shouldn't be elevated to a library function.
ok.
fwiw I'm looking at a r.watershed map with one color as 27:36:70, fairly
dark.
> If you just want to eliminate dark or saturated colours,
this is the core of the wish I suppose,
> it would be preferable to add transformation functions to adjust
> and/or clip the intensity, saturation and hue, which could then
> be applied to any existing colour rule, not just random colours.
r.colors -m # for "mute"
?
It would be a nice excuse to create proper G_hsv2rgb() and G_rgb2hsv()
fns. ie calculate hue angle using real sine/cosine, not just use the
hexagon approx to the circle.
http://www.mandelbrot-dazibao.com/HSV/HSV.htm
I am also a little confused in my r.cpt2grass GMT color scale -> GRASS
colr/ rules converter: "value" = 0.0 is white, but is 1.0 black and 0.5
"maximum"? or is 1.0 full-scale color? Some of the GMT rules
(/usr/share/gmt/cpt/GMT_topo.cpt) have S all < 0.5 and look washed out
with my script unless you do S*=2. And another (GMT_sealand.cpt) has value
all = 1.0, and AFAICT that all becomes black?
http://article.gmane.org/gmane.comp.gis.grass.user/23635/
http://trac.osgeo.org/grass/browser/grass-
addons/raster/r.colors.tools/r.cpt2grass
Maybe I just have to elevate my brain sugar and study it again.
(eg mixing up S and V and/or HSV and HIS)
the wikipedia page on it suggests V=0.0 is white and 1.0 is black.
http://en.wikipedia.org/wiki/HSL_and_HSV
shrug.
but I digress,
Hamish
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Ticket URL: <http://trac.osgeo.org/grass/ticket/170#comment:3>
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