Setting ColorScale to log makes imagesc show wrong colors

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Hello all !
I've encountered a discrepancy within my imagesc figure between the value of the Index of a point and the color it is supposed to be according to the colorbar within my code.
I managed to reproduce this "error" using a simple script that you can try :
MyImage = pascal(10);
figure
hold on
im=imagesc(1:10,1:10, MyImage);
set(gca,'ColorScale','log')
h = colorbar;
colormap(hsv(5))
As you'll notice some squares do not have the color that it should have according to the colorbar, for example the point [X,Y]=[3 9] has index 45, which should be Yellow according to the colorbar, yet it is in red. Same with [X,Y]=[7 6] with index 462 appears yellow but should be green. There are several other points that have this discrepancy.
When I remove the "set(gca,'ColorScale','log')" line there doesn't appear to be this issue (even more obvious with my original images) so I suspect the error is related to this.
I'm not sure what I've done wrong, I have spent hours ripping my hair over this so any help is much appreciated.
Many thanks.
  2 Comments
Aurelien Gregor
Aurelien Gregor on 27 Jul 2021
I managed to find an interesting answer here https://fr.mathworks.com/matlabcentral/answers/737702-how-to-get-logarithmic-colorbar-in-matlab-r2012a-for-3d-surface-plot which seems relevant to my issue although I am not sure if I understand it correctly.
Any help in applying this method to my code would be greatly appreciated.

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