On 2009-08-19 15:11-0500 Hezekiah M. Carty wrote:

> I would like to add support for loading segmented colors scales with
> plspal1, using plscmap1a rather than plscmap1la.  This way, the colors
> would be separated by distinct cut-offs rather than continuous
> transitions.  See the color bar used by the US National Weather
> Service radar images as an example:
>
> http://radar.weather.gov/ridge/radar.php?rid=lsx&product=N0R&overlay=11101111&loop=no
>
> This is a fairly straightforward change, and I have prepared it
> locally.  However, two approaches seem reasonable to me and I would
> like to as for others' opinions before settling on one.
>
> The first, and the one I have implemented, is a new file format.
> Rather than a "v2" header, this one has a "v2s" header (s =
> segmented).  No reverse field is needed, as it is not applicable here.
> This format is otherwise the same as the existing v2 format.
>
> The second option I thought of after implementing the v2s file format
> code is to change the plspal1 API to take a second argument to
> determine if the file should be interpreted as discrete values or
> interpolation points.  Something similar to "plspal1(filename, true)"
> for an interpolated color map and "plspal1(filename, false)" for a
> segmented color map.
>
> I like the second option more because the same color palette files can
> potentially be used for multiple purposes.  It does, however, require
> a small API change to plspal1 (adding a PLBOOL parameter) which would
> then have to be propagated to all the language bindings.
>
> Any thoughts?  I understand that this is rather poor timing, given the
> number of "added plspaln to language X bindings" Subversion commits
> there have been recently.  This has unfortunately been my first chance
> to dig in to this section of code and see how it works.

I couldn't get the above link to work for me so I am having some trouble
envisaging what you want to do.  Just to confirm I understand what you are
proposing, will you be calling plscmap1a as an alternative to plscmap1la
within plspal1 for the discrete case?

Assuming we all agree this is a worthwhile thing to do, now (i.e., before
our first official release with plspal1) is the time to be changing the API
rather than after the release.  I would be willing to help you with
the propagation work so let's not be concerned about that prospect, and
instead make sure we have the API we want.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); 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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