intlut() alternative for LUT consisting of doubles
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Is there a fast alterative to intlut() accepting an array of doubles as LUT?
Problem is, I want to convert grayscale values (uint8) of an image using a LUT consisting of 256 doubles.
Example:
lut = (1:256)+0.1; % upshift by 0.1
A = uint8(randi(256,50));
% current approach
lutMat = repmat(reshape(lut, 1, 1, numel(lut)), ...
size(A));
idx = sub2ind( ...
size(lutMat), ...
repmat((1:size(A, 1))', 1, size(A, 2)), ...
repmat((1:size(A, 2)) , size(A, 1), 1), ...
double(A));
B = lutMat(idx);
The above code works fine, but takes a lot of time and needs too much memory
3 comentarios
Image Analyst
el 20 de Ag. de 2012
You're still having the problem? Didn't my code do what you want?
Respuestas (2)
Jan
el 18 de Ag. de 2012
I'm not sure if I understand the question. Does this help:
B = lut(A);
0 comentarios
Image Analyst
el 18 de Ag. de 2012
Editada: Image Analyst
el 18 de Ag. de 2012
If you're just adding a constant value to the lut-transformed values, like 0.1, you can just do this:
lut = uint8(1:256); % upshift by 0.1
A = uint8(randi(256,50));
B = double(intlut(A, lut)) + 0.1;
If it's not some constant added value, then you can do it like this:
lut = 1000 * rand(256, 1); % A Random reassignment between 0 and 1000.
A = uint8(randi(256,50));
B2 = zeros(size(A), class(lut));
for inputValue = uint8(0) : uint8(255)
indexes = (A == inputValue);
B2(indexes) = lut(inputValue + 1);
end
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