Region Labelling
Asked by Adam on 8 May 2012
Latest activity Answered by Image Analyst on 8 May 2012
I would like to extract the lungs from an image, but as I'm new to matlab im unsure of how to go around this.
So far I have this:
i=imread('Image1.png');
t=graythresh(i);
i2= im2bw(i,t);i3= edge(i2,'sobel');
imshow(i3)
bw2 = imfill(i4, 'holes');
imshow(bw2)L = bwlabel(bw2);
% colouredLabels = label2rgb(L, 'hsv','k','shuffle');
Ex = regionprops(L, 'Centroid');
hold on ;
for k = 1:numel(L)
c = Ex(k).Centroid;
text(c(1),c(2),sprintf('%d',k),'HorizontalAlignment','center', 'VerticalAlignment','middle');end
This so far, shows the thresholded image with each region labeled. What I'm trying to do is find and display the lungs, which would be over a certain area.
I've attempted to use something like his:
allowableAreaIndexes = allBlobAreas > 100;
combined with a couple other lines, but to no luck...
Would anyone be able to tell me how to go around this problem?
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1 Answer
Answer by Image Analyst on 8 May 2012
You need to use ismember() as explained in my image segmentation tutorial: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862 Here's the relevant snippet of code:
% Get a list of the blobs that meet our criteria and we need to keep.
allowableIntensityIndexes = (allBlobIntensities > 150) & (allBlobIntensities < 220);
allowableAreaIndexes = allBlobAreas < 2000; % Take the small objects.
keeperIndexes = find(allowableIntensityIndexes & allowableAreaIndexes);
% Extract only those blobs that meet our criteria, and
% eliminate those blobs that don't meet our criteria.
% Note how we use ismember() to do this.
keeperBlobsImage = ismember(labeledImage, keeperIndexes);
% Re-label with only the keeper blobs kept.
labeledDimeImage = bwlabel(keeperBlobsImage, 8); % Label each blob so we can make measurements of it
% Now we're done. We have a labeled image of blobs that meet our specified criteria.
subplot(3, 3, 7);
imshow(labeledDimeImage, []);
title('"Keeper" blobs (3 brightest dimes in a re-labeled image)');
Adapt it in the obvious ways (take out stuff about intensities, take out subplots, etc.).
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