imagesc Make all zeros white and all <zeros grey

Question

Robert 2015-9-25

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/244955-imagesc-make-all-zeros-white-and-all-zeros-grey

回答： Walter Roberson 2015-9-25

I asked a very similar question a few hours ago and was given the answer I was looking for at the time, but I have jsut realized that I need to slightly modify my question

previous question here http://www.mathworks.com/matlabcentral/answers/244945-imagesc-make-all-zeros-white

I have successfully made all the zeros in my imagesc plot white using the following code

figure(1)
imagesc(testNSE);
title ('Model vs Observations All NSE')
caxis([0, 1])
myColorMap = jet(256);
myColorMap(1,:) = 1;
colormap(myColorMap);
colorbar

however I have just realized that this makes all zeros and values <zero white. Now I need all zeros white and all <zeros gray (or another specified color). The colorbar should still only maintain a scale from 0-1.

I have tried creating multiple colourmaps but have had no success and now I am stuck

Thank you in advance for any help

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Answer 1

Walter Roberson 2015-9-25

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https://ww2.mathworks.cn/matlabcentral/answers/244955-imagesc-make-all-zeros-white-and-all-zeros-grey#answer_193682

在 MATLAB Online 中打开

I had to make an arbitrary choice about what to do with the data that is greater than 0 but small enough that it would quantize down to one of the reserved slots, so I moved it all to the first non-reserved slot.

cmap = jet(256);
cmap(1,:) = 0.8;
cmap(2,:) = 1;
cmapsize = size(cmap,1);
maxval = max(testNSE(:));
scaledNSE = (testNSE / maxval) * cmapsize;   %could be negative or 0
smallNSE = (scaledNSE > 0 & scaledNSE < 3);
scaledNSE(testNSE < 0) = 1;
scaledNSE(testNSE == 0) = 2;
scaledNSE(smallNSE) = 3;
image(scaledNSE);    %caution: imshow() or imagesc() might give different results
colormap(cmap);
caxis([0 cmapsize-1])