Here is the behavior I see on a plplot build (a bit old but none of this stuff
has changed recently AFAIK). BTW H=120 is green, blue is H=240. Cf.
http://en.wikipedia.org/wiki/HLS_color_space
Using a Hue range of {0,120} gives a Red - Yellow - Green shading.
Using a Hue range of {120,0} gives a Green - Yellow - Red shading.
Selecting rev=1 causes the interpolation to go around "the back side" of the
color wheel, yielding in the latter case Green - Cyan - Blue - Magenta - Red.
So from my perspective it's working as expected, aside from the "rev" misnomer
("back" or "wrap" would've been better -- my bad).
Maurice
On Friday, August 10, 2012 at 03:04:22 (-0700) phil rosenberg writes:
> Hi all
> I've come across a "feature" of the cmap1 colourscale that I wanted to
> check. According to the doumentation for plscmap1l "the hue is interpolated
> around the front of the colour wheel (red-green-blue-red) unless the rev
> flag is set to true.
>
> I've found however that this isn't always the case and that reversing the
> order of points on the coord arrays also reverses the direction. For example
> using HLS I set coord1 to {0,120} and rev to false which gives me a
> colourscale of red-yellow-green-turquoise-blue. If I then set coord1 to
> {120,0} I would expect to get a colourscheme from blue-purple-red, but
> instead I get blue-turquoise-green-yellow-red.
>
> I've called it a feature, because I'm not sure if this is a bug in the code
> or if it is the correct behaviour but the documentation isn't great. Any
> thoughts?
>
> Phil
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