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

[<jc...@fe...>]

On Saturday 06 July 2002 01:47, Alan W. Irwin wrote:
| 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?

the xfig file format stores colors at a fixed position (variable length)=20
in the begining of the file; latter changes in the colors will thus=20
overwrite the previous color setting, thus the observed results.

I think the same happens for any file based format, and can't be fixed.

Jo=E3o

|
| Alan
|
| email: ir...@be...
| phone: 250-727-2902=09FAX: 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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