more than 256 colors in colormap no longer working
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I wondered if anyone has seen this before?
if i use: figure; imagesc(randn(256)) colormap(jet(256))
the image is displayed as i would expect with 256 graduations in the jet color scheme.
but if i change to colormap(jet(300)) it starts to mess up the color map and if increase higher, I end up, eventually, with one colour in the color map.
This used to work fine, and still works on my linux versions of matlab (i think it's 2011a), but on the 64 bit version on windows (both 2011a and 2012a on windows 7) it messes up.
This is causing some grief as i have some plotting functions that use custom colormaps with a large number of colors which no longer work.
anyone any idea why?
Cheers
Richard
2 commentaires
Jan
le 6 Sep 2012
Does this concern e.g. http://www.mathworks.com/matlabcentral/fileexchange/37971-colormaps-with-higher-bit-depth, which has been developped under 2012a?
Peter
le 14 Oct 2013
The linked page that contained the answer has somehow been taken offline. Would anyone still have that answer?
Réponses (2)
Doug Hull
le 6 Sep 2012
Currently, there is a 256 row colormap limit on the PC platform. The workaround is to manually reduce the colormap length, by consolidating colors that are "close enough" into one color. The Image Processing Toolbox contains routines for accomplishing this. Our developers are aware of this limitation and are investigating other possible workarounds.
Richard Smith
le 10 Oct 2012
2 commentaires
Dennis
le 3 Jan 2014
Thanks Richard Smith! Your workaround works for me as well (R2013b 64bit). I do think matlab should solve this issue with their default renderer...
John Ebersole
le 6 Fév 2015
This is great! I've been looking for a while for this.
I perform gamma correction whenever I plot images, so for a PC with a gamma of 2.2, the following looks great:
imagesc(myimage); axis image; colormap(gray(8192).^(1/2.2)); set(gcf,'renderer','OpenGL')
If I only use 256 instead of 8192, deep grays turn black too easily.
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