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An object with the biggest amount of scope in the Binary image

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Felix
Felix on 12 Sep 2013
Hello, I have a binary image with n white objects (not connected). How can I leave only the object with the biggest amount of scope in the picture I can do it by - bwareaopen, but in this way I have to know approximate size of an object. sorry for my english. thnx

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Accepted Answer

Image Analyst
Image Analyst on 13 Sep 2013
Try this:
grayImage = imread('coins.png');
subplot(2,2,1);
imshow(grayImage);
binaryImage = grayImage > 100;
binaryImage = imfill(binaryImage, 'holes'); % Fill holes.
[labeledImage, numObjects] = bwlabel(binaryImage);
stats = regionprops(labeledImage,'Area');
allAreas = [stats.Area]
[~, indexOfLargest] = max(allAreas);
largestBlob = ismember(labeledImage, indexOfLargest)>0;
subplot(2,2,2);
imshow(largestBlob);
title('Largest');
keeperIndexes = 1:numObjects;
keeperIndexes(indexOfLargest) = [];
binaryImage2 = ismember(labeledImage, keeperIndexes)>0;
subplot(2,2,3);
imshow(binaryImage2);
title('All Except Largest');

More Answers (2)

Adam Filion
Adam Filion on 12 Sep 2013
Edited: Adam Filion on 12 Sep 2013
If you have Image Processing Toolbox you can use the function regionprops. It comes out to something like this, where tm is the binary image.
cc = bwconncomp(tm);
stats = regionprops(cc,'Area');
A = [stats.Area];
[~,biggest] = max(A);
tm(labelmatrix(cc)~=biggest) = 0;
You can watch a recorded presentation that steps through a similar example here:

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Felix
Felix on 12 Sep 2013
Thanks for the help, it close enough to what I asked, however, it erased all the small arias except the closest ones to the object . can you tall me why is that? sorry i can't upload an image, can i send it to your e-mail?

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Sean de Wolski
Sean de Wolski on 17 Sep 2013
Good timing, I just posted this function a few minutes ago!

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