Re: plot_image color tables

Hi Joey,

I spent to much time to prepare my answer with an advertisement...
But I send my post even though the problem is already solved. ;-)

I was about to say that I can't think that PGPLOT's plot_image is able 
to perform such a task, but I found that it indeed is!
ISIS' PGPLOT module offers the S-Lang function _pgctab as a wrapper for 
http://www.astro.caltech.edu/~tjp/pgplot/subroutines.html#PGCTAB.
You can use it, e.g., as
    _pgctab([0,1], [0,.8], [0,0], [0,1], 1, .5);
to ramp red from 0 to .8, keep green at 0 and ramp blue from 0 to 1, 
intentionally avoiding the (r,g,b)=(1,0,1) pink... ;-)

Through this exercise, I also learned the solution to another problem I 
had for a long time: I could not use plot_image to write ps files, and I 
had always thought PGPLOT is to blame. But it actually works when I call 
this _pgctab or just set_palette(0); after open_plot! Did anybody else 
have this problem, too?


The way I would usually address this task (and still will, despite that 
I now know that PGPLOT could do it...) is to write a png file in the 
colors I want and then use John Davis' SLxfig module to include it into 
*a wonderful plot*, with code as simple as
   variable p = xfig_plot_new();
   p.world(xmin, xmax, ymin, ymax);
   p.plot_png(pngfilename);
   p.xlabel(xlab);
   p.ylabel(ylab);
   p.render("a_wonderful_plot.eps");  % which ever
   p.render("a_wonderful_plot.png");  %  you like
   p.render("a_wonderful_plot.pdf");  %    most

Although SLxfig is still pre-version 0.2, I think it is already quite 
powerful. If you want to convince yourself: John has nice examples on 
http://www.jedsoft.org/fun/slxfig/examples.html, and I've recently put 
those from the source code itself on 
http://pulsar.sternwarte.uni-erlangen.de/hanke/science/X-ray/ISIS/SLxfig/. 
(You can also find a link to my institute's wiki there, which contains a 
few further examples.)
Last but not least, I'd like to advertise Thomas' accretion disks in 
http://adsabs.harvard.edu/abs/2010MNRAS.409.1534D.

Cheers,

Manfred, indeed a passionate SLxfig user... :-)


P.S.  A happy new year to all ISIS users!


Joseph Neilsen wrote:
> Hi,
>
> I'm wondering if there is a way to use plot_image to make images of an
> arbitrary color. I have a 2D Gaussian that I'm trying to display, and I'd
> like to do it in various levels of purple (i.e. purple fading to black).
> set_palette allows you to select the color table, but not to just pick a
> color.
>
> Is there a way to do what I'm looking for?
>
> Thanks!
>
> Joey
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