[Plplot-devel] rgb colourscale interpolation

[Alan W. I. <Ala...@gm...>]

Hi Phil:

I am moving this discussion to plplot-devel where it belongs.

I think your backwards-incompatible changes [h,l,s ==> c1,c2,c3
changed member names] in the PLControlPt struct are likely a good idea
since h,l,s was a misnomer.  Nevertheless, those changes did cause
important build problems in the Tk-related part of the build which I
have now fixed (commit 94e2e5b01).

Example 12 (which uses RGB interpolation) shows the effect of your
change.  The old code produced
<http://plplot.org/examples-data/demo12/x12.01.png> which shows fairly
discontinous colour results from 1982 to 1986, while the new code
produces much smoother colour changes in that date range.  So from
this evidence I feel your change is a nice win.

I previously said (in response to your question about how you
should edit README.release):

> I assume you will want to insert a paragraph concerning
your change in a new section 2.8 of "Improvements relative to the
previous release".  Also, since you changed the semantics of the two
functions (although not their API) for the RGB case you should
probably specifically warn the users of this forthcoming release about
that semantics change by adding a one-sentence new section 1.10 in
"OFFICIAL NOTICES FOR USERS" that refers to your new section 2.8 for
the details.

Since your backwards-incompatible API change to the PLControlPt struct is going
to cause build problems (just like it did in our Tk-related code)
for the minority of our users who actually use that struct
in their code, you should expand that suggested single sentence in 1.10 to
warn users of this specific change to PLControlPt.

I look forward to your commit with the suggested changes in README.release.

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).
__________________________

Linux-powered Science
__________________________