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[Octave-bug-tracker] [bug #52624] gnuplot toolkit binary image is only b

From: Dan Sebald
Subject: [Octave-bug-tracker] [bug #52624] gnuplot toolkit binary image is only black pixels
Date: Tue, 12 Dec 2017 21:53:27 -0500 (EST)
User-agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:55.0) Gecko/20100101 Firefox/55.0

Follow-up Comment #4, bug #52624 (project octave):

I meant that I think both gnuplot and OpenGL toolkits aren't consistent with
Matlab.  Since gnuplot is adding 1 to cdata, I assume that is the same as what
FLTK is doing.  I don't see why for integers we'd add one but for doubles
(passed through fix) we wouldn't add one.  Logical I can understand--it makes
no sense for there to be only alternatives 0 and 1 when the colormap starts at

How did you generate these two scatterplot figures with the same data in both
the gnuplot toolkit and FLTK toolkit?  Re-calling the demo with a different
toolkit creates a different set of data.  I can probably figure this out by
writing a script similar to the northeast case, i.e., a single color in a
scatter plot.  It could be a "scaled" issue when the color map size is one
entry...in fact, that might be this case where "clim_rng" is 0 because there
is only a single color:

    if (clim_rng != 0)
      cdata = 255 * (cdata - clim(1)) / clim_rng;
      cdata(cdata < 0) = 0;  cdata(cdata > 255) = 255;
      cdata(:) = 255;

Maybe 255 is not the value to use.  I'll investigate...


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