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How to apply sift to each superpixel in image ?

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This implementation is to apply sift to an image that works correctly:
[Locations,Descriptors]= vl_sift(I);
Locations=Locations([2,1,3,4],:)';
Descriptors=Descriptors';
num_keypoint=size(Locations,1);
Descriptors=double(Descriptors);
Descriptors=Descriptors./repmat(NormRow(Descriptors,2),1,128);
And this is my implementation to apply sift to each superpixel, But I believe it's not right and ultimately leads to a false detection.
Locations=[];
Descriptors=[];
for p=1:num_segments
seg_map=(segments==p); % Specify each segment
% seg_map( ~any(seg_map,2), : ) = []; %rows
% seg_map( :, ~any(seg_map,1) ) = []; %columns
% seg_map=double(seg_map);
% seg_map(seg_map==0) = nan;
[yy,xx]=size(seg_map);
sift_segments = zeros('like',grayimage);
for i=1:yy
for j=1:xx
if seg_map(i,j)==0
sift_segments(i,j)= 0;
else
sift_segments(i,j)=grayimage(i,j);
end
end
end
II=single(sift_segments);
% II(II==0) = nan;
[Loc,Des]= vl_sift(II, 'PeakThresh', Sift_Treshold(p));
Loc=Loc([2,1,3,4],:)';
Locations=[Locations;Loc];
Des=Des';
Descriptors=[Descriptors;Des];
end
num_keypoint=size(Locations,1);
Descriptors=double(Descriptors);
Descriptors=Descriptors./repmat(NormRow(Descriptors,2),1,128);
Please pay attention to the lines that have been commented.
And the problem is that the location and descriptors extracted of each superpixel do not Correctly integrate into a matrix.
Have you got a solution?

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R2018b

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