[Octave-bug-tracker] [bug #54545] Images plotted with imshow are too bright with Gnuplot 5.0 and earlier

[Mike Miller]

Update of bug #54545 (project octave):

                Priority:              5 - Normal => 3 - Low                
                  Status:                    None => Confirmed              
                 Release:                   4.2.2 => dev                    

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Follow-up Comment #1:

Confirmed with Octave 4.4 and the development version, using gnuplot 4.6.

Also confirmed that https://hg.savannah.gnu.org/hgweb/octave/rev/d8626fd6bb36
is responsible for this regression with older gnuplot, and that restoring the
line


--- a/scripts/plot/util/private/__gnuplot_draw_axes__.m
+++ b/scripts/plot/util/private/__gnuplot_draw_axes__.m
@@ -2847,6 +2847,8 @@ function cdata = mapcdata (cdata, mode, 
     else
       cdata(:) = fix (255 / 2);
     endif
+    ## Scale using inverse of gnuplot's cbrange mapping
+    cdata = 1 + cdata * (cmap_sz-1)/255;
   else
     if (strcmp (mode, "scaled"))
       clim = double (clim);


restores the previous behavior, obviously while breaking gnuplot 5.2 and
newer.

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  <https://savannah.gnu.org/bugs/?54545>

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