MATLAB: I have a 2400×2400 matrix that I would like to use as a mask for each layer of a 2400x2400x46 matrix. Since the matrix dimensions are not equal, I cannot do so by simply multiplying the mask matrix by the larger matrix. How might I do this

applying 'mask' matrices to matrix of unequal dimensions

I have a 2400×2400 matrix that I would like to use as a mask for each layer of a 2400x2400x46 matrix. Since the matrix dimensions are not equal, I cannot do so by simply multiplying the mask matrix by the larger matrix. How might I do this? The end goal is to have a 2400x2400x46 matrix that has "NaN" for all "NaN" values in the mask matrix.

Thank you.

Best Answer

% Mask the image.
maskedHyperSpectralImage = bsxfun(@times, HyperSpectralImage, cast(mask,class(HyperSpectralImage)));

Note: the above is all one line of code.

Related Solutions

MATLAB: How to assign NaN in matrix by masking

Logical indexing is your friend! find() is a little slow because it can't predict how many matches there will be, so it can't preallocate the output vectors and keeps resizing those vectors every time a new match is found.

The "logical" solution:

matrix1(~(matrix2 == mask)) = nan

(matrix2 == mask) is a boolean matrix, with 1 indicating it matches the mask. The ~ operator flips the 0's and 1's, so 1 indicates it doesn't match the mask. And you can supply this matrix as the indices to matrix1, and assign nan as the scalar.

MATLAB: Creating a “mask” over an image

See these snippets:

% Extract the individual red, green, and blue color channels.
redChannel = rgbImage(:, :, 1);
greenChannel = rgbImage(:, :, 2);
blueChannel = rgbImage(:, :, 3);
% Create the mask
mask = greenChannel > n;
% Mask image must be converted to the same integer type
% as the integer image we want to mask.
mask = cast(binaryImage, class(rgbImage));
% Masking method #1:
% Multiply the mask by each color channel individually.
maskedRed = redChannel .* mask;
maskedGreen = greenChannel .* mask;
maskedBlue = blueChannel .* mask;
% Recombine separate masked color channels into a single, true color RGB image.
maskedRgbImage = cat(3, maskedRed, maskedGreen, maskedBlue);
% Masking method #2:
% An alternate method to multiplication channel by channel.
% Mask the image using bsxfun() function
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask, class(rgbImage)));

Best Answer

Related Solutions

MATLAB: How to assign NaN in matrix by masking

MATLAB: Creating a “mask” over an image

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