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How to calculate the contrast energy, entropy of a ROI(Region of interest) of an image using GLCM feature extractactions method?

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Elias Unk
Elias Unk on 5 Jun 2017
Commented: Binu on 8 May 2020
I need to extract GLCM features like energy entropy contrast among others of the REGION OF INTEREST ONLY excluding the black background,i managed to extract those features for the entire image but i only need them for the region of interest knowing that everything else will be black
% Loop over all GLCMs
for k = 1:nglcm
currentGLCM = glcm(:,:,k);
glcmMean(k) = mean2(currentGLCM);
% For symmetric GLCMs, uX = uY
uX(k) = sum(I.*currentGLCM(sub));
uY(k) = sum(J.*currentGLCM(sub));
sX(k) = sum((I-uX(k)).^2.*currentGLCM(sub));
sY(k) = sum((J-uY(k)).^2.*currentGLCM(sub));
out.contrast(k) = sum(abs(I-J).^2.*currentGLCM(sub)); %OK
out.dissimilarity(k) = sum(abs(I - J).*currentGLCM(sub)); %OK = sum(currentGLCM(sub).^2); % OK
out.entropy(k) = -nansum(currentGLCM(sub).*log(currentGLCM(sub))); %OK
out.inverseDifference(k) = sum(currentGLCM(sub)./( 1 + abs(I-J) )); %OK
out.homogeneity(k) = sum(currentGLCM(sub)./( 1 + (I - J).^2)); %OK

Answers (3)

Phuong Nguyen
Phuong Nguyen on 3 Apr 2020
Did you solve this problem? I am having the same problem with you and cant get over it. If you done, could you please teach me? Thank you.
  1 Comment
Binu on 8 May 2020
Force all pixel values outside your region of interest as a 'NaN'. The graycomatrix methods by default ignores any pixel pairs having a 'NaN' value.

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Binu on 4 Aug 2017
The graycomatrix function has a '*GrayLimits*' argument where you can specify a two-element vector [low high] which is used for scaling the image and creating NumLevels. Grayscale values less than or equal to low are scaled to 1. You could set that yours to [0.1 1] for your case.

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