draw oriented rectangle around a blob

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function y=cadre(x)
info = regionprops(x,'Boundingbox') ;
imshow(x)
hold on
for k = 1 : length(info)
BB = info(k).BoundingBox;
rectangle('Position', [BB(1),BB(2),BB(3),BB(4)],'EdgeColor','g','LineWidth',1) ;
end
I am using this code with a segmented image in input, and I have this result :
input output
I would like the rectangles to be the smallest and with the same orientation as the objects, to get the angles for exemple.
How can I modify my code ?

Risposta accettata

Scott MacKenzie
Scott MacKenzie il 27 Mar 2022
Modificato: Scott MacKenzie il 27 Mar 2022
Something like this seems to work:
img = imread('testimage.jpg');
bw = imbinarize(im2gray(img),'adaptive','Sensitivity',0.45);
info = regionprops(bw, 'all');
imshow(img);
hold on;
minSize = 50; % ignore small/noise regions (adjust as necessary)
angles = [];
for k = 1:length(info)
% get region properties
w = info(k).MajorAxisLength;
h = info(k).MinorAxisLength;
x = info(k).Centroid(1) - w/2;
y = info(k).Centroid(2) - h/2;
theta = info(k).Orientation;
if h < minSize % skip the small/noise regions
continue;
end
angles = [angles theta];
ps = polyshape([x, x, x+w, x+w], [y, y+h, y+h, y]);
ps2 = rotate(ps, -theta, [x+w/2 y+h/2]);
plot(ps2, 'EdgeColor','r', 'FaceColor','none', 'LineWidth',2);
end
angles
angles = 1×2
67.7787 -44.8710
  1 Commento
Image Analyst
Image Analyst il 27 Mar 2022
OK but note that the boxes don't completely contain the blobs.

Accedi per commentare.

Più risposte (2)

Image Analyst
Image Analyst il 26 Mar 2022

Walter Roberson
Walter Roberson il 26 Mar 2022
Modificato: Walter Roberson il 26 Mar 2022
Note that if you are looking for the angles then regionprops() 'Orientation' will give you the angle of the major axes.

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Release

R2022a

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