You can use bwconncomp. See this demo I wrote for you:
U3(:,:,1) = [
0 , 0 , 0 , 0 , 0;
0 , 0 , 0 , 0 , 0;
0 , 1 , 0 , 0 , 1;
0 , 0 , 0 , 0 , 0;
0 , 0 , 0 , 0 , 0
]
U3(:,:,2) = [
0 , 0 , 0 , 0 , 0;
0 , 0 , 0 , 0 , 0;
0 , 1 , 0 , 0 , 1;
0 , 1 , 0 , 0 , 0;
0 , 1 , 0 , 0 , 0
]
U3(:,:,3) = [
0 , 0 , 0 , 0 , 0;
0 , 0 , 0 , 0 , 0;
0 , 1 , 0 , 0 , 1;
0 , 0 , 0 , 0 , 0;
0 , 0 , 0 , 0 , 0
]
% Method 1
% Make the list for how you want the objects labeled:
desiredNumberList = [2 3 4 42 69 123 73]; % Whatever you want.
% Make an object for the output
labeledImage = zeros(size(U3), 'int16')
% Do connected components labeling.
connectivityObject = bwconncomp(U3)
% Get the number of object it found (optional).
numberOfObjects = connectivityObject.NumObjects
% Now go through the blobs, reassiging them with the labels Hisham wants.
for blob = 1 : numberOfObjects
% Get the linear indices of the pixels that
% identify this particular blob.
pixelIndexes = connectivityObject.PixelIdxList{blob}
% Make those pixels have the desired number.
labeledImage(pixelIndexes) = desiredNumberList(blob);
end
% Print out the output image to the command window.
labeledImage
% Method 2
% Use labelmatrix but cast to uint16 if you ever expect to have more than 255 blobs.
labeledImage = uint16(labelmatrix(connectivityObject))
% But you didn't want 1,2,3, etc. You wanted custom numbers.
% For that we need to remap the default label numbers using intlut().
% Right now the blobs are labeled 1,2,3, etc.
% Make those pixels have the desired number with intlut().
% Make the list for how you want the objects labeled:
% But first one has to be zero because zero must remain as zero.
desiredNumberList = zeros(1, int32(intmax('uint16'))+1, 'uint16');
desiredNumberList(1:8) = [0 2 3 4 42 69 123 73]; % Whatever you want.
labeledImage = intlut(labeledImage, desiredNumberList)
