Remove everything outside of largest circle found by regionProps

Hello!

So I followed this example here: RegionProps and I was wanting to take the largest circle found and to segment out / clear everything else from the image.

Is there a straight forward way to do this, or rather a Matlab method of doing it?

Many thanks for any help!

Answer 1

[Walter Roberson]

   YourRGBImage = .... original image
   ROI = .... after threshholding
   props = regionprops(ROI, 'Area, 'PixelIdxList');
   [~, idx] = max([props.Area]);
   this_region = props(idx).PixelIdxList;
   mask = zeros(size(ROI), class(YourRGBImage));
   mask(this_region{:}) = 1;
   mask = mask(:,:,[1 1 1]);   %replicate to 3D
   masked_Image = YourRGBImage .* mask;

Answer 2

[Image Analyst]

Before you call regionprops, simply call bwareafilt() on bw:

bw = bwareafilt(bw, 1); % Extract largest blob.

This will keep (segment out) only the largest circle in the image.