Unable to perform assignment because the left and right sides have a different number of elements.

I am attempting to swap the pixels of the brightest with the darkest in the image. I get this error but as far as I know they have the same number of elements. I check with numel.

[Jan]

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Answer 1

[the cyclist]

The assignment will only have the same number of elements if maskMax3D and maskMin3D have the same number of TRUE elements. For example, with smaller matrices, so that we can see what is going on:

% Note that these masks do not have the same number of TRUE elements
mask1 = logical([1 1; 1 0]);
mask2 = logical([1 0; 0 1]);

M1 = [2 3; 5 7];
M2 = [11 13; 17 19];

% Therefore these two arrays do not have the same number of elements, and
% cannot be assigned to each other
M1(mask1)

ans = 3×1

2 5 3

M2(mask2)

ans = 2×1

11 19

Answer 2

[Image Analyst]

Not sure what you mean because your question is not complete (no code, no images, no good explanation). Maybe it's this

yourImage = 255 - yourImage;

If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:

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