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

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

Answer 1

[Image Analyst]

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');

[Felix]

thank you! it's good!

Answer 2

[Adam Filion]

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:

https://www.mathworks.com/company/events/webinars/wbnr60402.html

[Felix]

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?

[Image Analyst]

Try uploading an image to http://snag.gy or http://tinypic.com.

Answer 3

[Sean de Wolski]

Good timing, I just posted this function a few minutes ago!

SCd:keepMaxObj