On 2018-07-25 10:13+0100 Phil Rosenberg wrote:
On 24 July 2018 at 20:19, Alan W. Irwin <alan.w.irwin1...@gmail.com> wrote:
[.... O]one concern I have about the current documentation, is
the documentation of the plscmap1la and plscmap1l alt_hue_path
argument. That argument makes a lot of sense in HLS space, but does
it make any sense at all if you are doing all interpolation in RGB
space? That is, should that argument be completely ignored if you are
using RGB space interpolation?
If I remember correctly, the point of alt_hue_path is specifically to
determine the direction around the colour wheel for interpolation once
the rgb values have been converted to hls. When supplying colours in
hls space, you can specify the direction by using hue values outside
the range of 0-360, for example specifying the two hues 0 and 240
would go from red to blue via yellow, green and cyan, whereas
specifying the two hues 0 and -120 would go from red to blue via
magenta. However if you specify rgb colours [1,0,0] and [0,0,1] then
you can use the alt_hue_path to tell plplot to interpolat backwards
round the colour wheel.
Hi Phil:
I believe your interpretation of what goes on with this argument for
the HLS case is correct.
So moving to rgb interpolation for rgb values makes this variable
defunct really.
I am pretty sure that is the case, but, of course, you should check for the
RGB case in your update to the code that this argument is completely ignored.
I guess the best thing is to simply state this in the
documentation?
Yes.
Can we deprecate it somehow and in a future release
remove it altogether?
This would require splitting each of the current plscmap1l and
plscmap1la functions into two in a backwards-incompatible way with one
for the HLS case (where alt_hue_path would be in the argument list)
and one for the RGB case (with no alt_hue_path in the argument list).
Thus, I think our current C API is the best choice so long as you
document that alt_hue_path is ignored for the RGB case.
I have made the code changes and am about to test them. I will then
make the documentation changes and commit the results today.
I look forward to seeing that commit.
Alan
__________________________
Alan W. Irwin
Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
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Linux-powered Science
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