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[Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imsho
From: |
Dan Sebald |
Subject: |
[Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow |
Date: |
Wed, 6 Dec 2017 18:05:12 -0500 (EST) |
User-agent: |
Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:55.0) Gecko/20100101 Firefox/55.0 |
Follow-up Comment #5, bug #52599 (project octave):
Yeah this could be a case of a change in gnuplot. I'm using the development
version 5.3.0.
There is this other bug report from a month or so ago:
https://savannah.gnu.org/bugs/?52401
at which point I looked into what was going on with gnuplot. gnuplot made a
change without too much discussion about syntax. Typically gnuplot is very
conservative about changing syntax. Rather than autoscaling to determine
range, gnuplot now has this "rgbmax" variable:
gnuplot> help rgbmax
Syntax:
set rgbmax {1.0 | 255}
unset rgbmax
The red/green/blue color components of an rgbimage plot are by default
interpreted as integers in the range [0:255]. `set rgbmax 1.0` tells the
program that data values used to generate the color components of a plot
with `rgbimage` or `rgbalpha` are floating point values in the range [0:1].
`unset rgbmax` returns to the default integer range [0:255].
If anything, I wish the syntax change would have been "set rgbrange [0:255]"
which would have been fully consistent with other range settings in gnuplot.
Nonetheless, gnuplot now has 0 to 255 as the default range and that is
probably why this comes up now.
The good thing is that I just went back to the example of
https://savannah.gnu.org/bugs/?52401 and changing the color map size to 256
octave:1> I=uint8(zeros(16,16,3));
octave:2> for i=1:16; I(i,:,1)=i*16-1; end
octave:3> for i=1:16; I(:,i,2)=i*16-1; end
octave:4> for i=1:16; I(:,i,3)=[i-1:15,0:i-2]*16+15; end
octave:5> imshow(I)
octave:6> colormap(jet(256))
appears to correct the image darkness. So, I'd say if the changeset has no
affect on your result with gnuplot 5.0.3 (because that is using autoscaling),
then it would be a good fix for the issue without using gnuplot's new "rgbmax"
syntax. We could then close this bug report and
https://savannah.gnu.org/bugs/?52401
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- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Francesco Potortì, 2017/12/06
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Dan Sebald, 2017/12/06
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Rik, 2017/12/06
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Dan Sebald, 2017/12/06
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Rik, 2017/12/06
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow,
Dan Sebald <=
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Rik, 2017/12/06
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Dan Sebald, 2017/12/07
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Francesco Potortì, 2017/12/07
- [Octave-bug-tracker] [bug #52599] gnuplot shows shaded images with imshow, Rik, 2017/12/07