[Plplot-devel] Problems with setting cmap0 and cmap1 for the xfig and png devices

[Alan W. I. <ir...@be...>]

Try the following experiment:

Make a special copy of x01c (or xw01.py, which is what I used) which calls
plscol0(1,255,255,255) between the first and second calls to plot1.  The
plscol0 call sets index 1 of cmap0 to white rather than the default red.

If you use interactive devices such as xwin, tk, ntk, etc. you get the
expected result; the first subplot of example 1 continues to have a red box,
red scales, etc., and the remaing sub-plots have white boxes and scales.

For the psc (colour postgrip) device the same result also occurs;
the first sub-plot has red box and scales, and the remaining subplots
have white box and scales.

However, for the xfig and png devices *all* the subplots unexpectedly have
white box and scales.  So if you change color indices part way through a
plot, the earlier part of the plot is retroactively changed for those
drivers!

The simple example I gave was for the discrete colours (cmap0), but I am
getting the same result for example 8 for the png driver with the continuous
colours (cmap1), and the results look quite bad.  At the end of that example
(which uses a gray-scale cmap1), I set cmap1 back to the default before
going on with plotting other plots for the tcl and python front ends.  (If I
don't do this, example 16 becomes gray scale rather than the desired default
colours since python and tcl run all examples under a common plinit.) This
procedure of resetting to default cmap1 works well for the psc device, but
for the xfig and png devices, resetting cmap1 to the default at the end
retroactively changes the whole continuous color map of example 8 back to
default (rather than leaving it at the desired gray scale).

So for both the xfig and png devices (and presumbably jpeg as well) we have
a nasty "retroactivity" problem with any attempt to change either cmap0 or
cmap1 part way through a plot.

Joao and Andrew, would you be willing to have a look at this problem for
your drivers (xfig.c for Joao and gd.c for Andrew) and fix it?

Alan

email: ir...@be...
phone: 250-727-2902	FAX: 250-721-7715
snail-mail:
Dr. Alan W. Irwin
Department of Physics and Astronomy,
University of Victoria, P.O. Box 3055,
Victoria, British Columbia, Canada, V8W 3P6
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