Mon 20 Nov 2017 07:59:23 PM UTC, comment #3:
Sorry for the delay on addressing this. I got to discussing this with the gnuplot developers, and the alteration and syntax chosen for gnuplot seemed clumsy so I guess I was hoping they'd see the sense in making syntax consistent, thereby avoiding changing something just to change it again a year from now. This gnuplot mod has me wondering.
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Mon 13 Nov 2017 05:10:48 PM UTC, original submission:
Hello,
Color images are far too dark when shown and exported using graphics_toolkit gnuplot. This equally affects imshow and imagesc, as well as any subsequent print, at least with octave 4.0.3 to 4.2.1, and with gnuplot 5.2.0 or later, including the current cvs version. However, colors are correctly shown with gnuplot 5.0.7 or earlier. Gray and B&W images are unaffected.
The following code reproduces the problem and generates a gnuplot file for testing.
After investigating, all this is due to the change introduced in gnuplot 5.2.0 regarding the use of cbrange. See the gnuplot ChangeLog:
Currently, octave uses set cbrange [1:64]; but this has no effect on rgb images since gnuplot 5.2, resulting in dark color images with any output device when handled through the gnuplot engine. Therefore octave should be updated to cope with the new gnuplot specifications.
The fltk graphics toolkit shows color images correctly but seems unable to export them, so it is not (yet) a valid solution (at least for me).
Hope this can be fixed.
Ricardo.
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