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imcrop a specific bounding box

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Oliver Ferenczi
Oliver Ferenczi on 24 Feb 2020
Answered: Josep Llobet on 24 Mar 2022
Hi, I am trying to write code that will crop around a specific bounding box on appdesigner. It currently works when there is only a single bounding box in the image. However when there are several it wouldn't know which box to crop around.
This is the current code.
bboxes = step(faceDetector, faceimage);
CroppedFaces = imcrop(app.Faces,bboxes);
Thank you
  1 Comment
Chaitanya Mallela
Chaitanya Mallela on 3 Mar 2020
if the faceDetector object has Bounding Box property, try to Label every Bounding Box and execute imcrop command in a loop whose max iteration value equals Number of Labels.

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Answers (1)

Josep Llobet
Josep Llobet on 24 Mar 2022
You can try the next code:
Obtain the image example
% __JUST OBTAIN THE IMAGE__%
% Obtain image
krillin = imread("https://es.mathworks.com/responsive_image/150/150/0/0/0/cache/matlabcentral/profiles/22817879_1627284404454.jpg");
% Process it
krillin_grey = im2gray(krillin);
krillin_grey_imadj = imadjust(krillin_grey);
krillin_BW = imbinarize(krillin_grey_imadj);
krillin_BW_2 = imclearborder(~krillin_BW);
% Labels (not necessary)
% krillin_BW_2_bwlab = bwlabel(krillin_BW_2);
% unique(krillin_BW_2_bwlab(:))
% imshow(krillin_BW_2_bwlab, [])
% Obtain the three major objects
krillin_BW_2_largest = bwpropfilt(krillin_BW_2, "Area", 3, "largest");
imshow(krillin_BW_2_largest)
Crop the Bounding Boxes
% __CROP THE BOUNDING BOXES__%
BB = regionprops(krillin_BW_2_largest,'BoundingBox'); %<--- rellevant
for every_BB = 1:length(BB)
BB(every_BB).BoundingBox;
krillin_BW_BB = imcrop(krillin, BB(every_BB).BoundingBox+[-1 -1 1 1]); %Es retalla la imatge basant-se amb el BoundingBox.
% change v'krillin' for v'krillin_BW_2_largest' for obtain the binary images of bounding box
figure
imshow(krillin_BW_BB)
end
From the image: you must obtain:

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