Distinct NaN from other values in image

Question

Agnete 2013-11-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106912-distinct-nan-from-other-values-in-image

评论： Dev Laxman Subramanian 2021-2-4

I want to plot image with different values and easily distinct them from NaN values. As default NaN values are imaged with the same color as the minimum value. I have tried a range of possibilites but each provide their own issue. Here is one example:

The solution from here, image all other values as one color

imagesc(CP)
sc(isnan(CP), 'bone', [1 1 1]);

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Image Analyst 2013-11-25

The answer has been accepted. I don't see a question in the last comment. And no m-file was attached.

Oliver Woodford 2014-1-2

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You did not use sc correctly. Try:

sc(CP, 'bone', 'r')

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Answer 1

Iain 2013-11-21

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https://ww2.mathworks.cn/matlabcentral/answers/106912-distinct-nan-from-other-values-in-image#answer_115938

在 MATLAB Online 中打开

This can let you plot NaN & any other logically findable section of the image as white

 a = rand(5);
 a(3,3) = NaN;
 b = imagesc(a);
 set(b,'AlphaData',~isnan(a))

Alternatively, you can deliberately control the "colormap" settings to ensure that "invalid" values show up as a colour that isn't used by the colour map.

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Andrea 2017-12-29

changed my life

Dev Laxman Subramanian 2021-2-4

Works like a charm!

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Answer 2

Image Analyst 2013-11-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/106912-distinct-nan-from-other-values-in-image#answer_115821

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I don't know what "plot" means when talking about an image. I don't know why you want to plot anything on an image, like markers to "cover up" the nan locations. Why not just set the nan's to the min gray level and view it like a normal image?

CP(isnan(CP)) = min(CP(:)); % Set nan values to the min value
image(CP);
colormap(bone(256));
colorbar;

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Agnete 2013-11-21

distinctNaNfromMinValue.pdf

The problem is illustrated in the attached where it is seen that the polygon in northeast corner blends into the background

Image Analyst 2013-11-22

Sorry but I don't understand this. One just sort of looks like a very blurred version of the other. Both have the same pattern of triangles on them, and I don't even know what a triangle means/represents. Your image is an array. You can't have nan values have the same value as your minimum value. An element can have only one value, either a nan or some number. It can't have both at the same time. So "Nan values are imaged with the same color as my minimum value" makes no sense to me.

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