MATLAB: Remove pixel and height that doesnt meet certain criteria

blobs

hi sir, in my color detection, I used ismember to set object between pixel 100 and 500. Its worked. however, can I know from the bounding box of object detection, how to remove bounding of blobs that doesnt meet height and width criteria ,say width and height of 100×100 pixels?

Best Answer

Sure, you just get all the bounding boxes

allBB = [blobMeasurements.BoundingBox];

Then extract every 4th one for the widths and heights.

allWidths = allBB(3:4:end);
allHeights = allBB(4:4:end);

Then use ismember just like you did to filter based on area. You'd do something like this:

% Get a list of the blobs that meet our criteria and we need to keep.
allowableWidthIndexes = (allWidths > 150) & (allWidths < 220);
allowableHeightIndexes = allHeights < 2000; % Take the small objects.
keeperIndexes = find(allowableWidthIndexes & allowableHeightIndexes );
% 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);

You can then relabel keeperBlobsImage and call regionprops on keeperBlobsImage if you want to measure only the keeper blobs.

Related Solutions

MATLAB: Extraction of rectangular blob from binary image

How about comparing length around the blob and length around the bounding box of the blob, like:

% sample blogs
I = imread('pillsetc.png');
Iblob = rgb2gray(I) > 200;
% measure perimeter and bounding box for each blob
stats = regionprops(Iblob,{'BoundingBox','perimeter'});
stats = struct2table(stats);
% extract the blob whose perimeter is close to round length of its bounding box
stats.Ratio = 2*sum(stats.BoundingBox(:,3:4),2)./stats.Perimeter;
idx = abs(1 - stats.Ratio) < 0.1;
stats(~idx,:) = [];
% show the result
imshow(Iblob);
hold on
for kk = 1:height(stats)
  rectangle('Position', stats.BoundingBox(kk,:),...
      'LineWidth',    3,...
      'EdgeColor',    'g',...
      'LineStyle',    ':');
end

MATLAB: How to divide height and width of 4 separate bounding boxes and compare it so that I can extract the object based on certain critera

Since you created the bounding boxes of the objects in the binary image, presumably with regionprops(), you already know their height and width of all the bounding boxes. You can keep certain ones by making a logical vector saying whether or not to keep it, then use that to extract only the ones you want to keep. For example if you only want widths > 30, you can do

props = regionprops(binaryImage, 'BoundingBox');
allBB = [props.BoundingBox];
allWidths = allBB(3:4:end);
keeperIndexes = allWidths > 30;
keeperProps = props(keeperIndexes);

Best Answer

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MATLAB: Extraction of rectangular blob from binary image

MATLAB: How to divide height and width of 4 separate bounding boxes and compare it so that I can extract the object based on certain critera

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