Drawing the major and minor axis of an elliptical object in Matlab
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LoserG G
el 2 de Abr. de 2012
Respondida: Image Analyst
el 3 de Jun. de 2024
This program currently inputs an image of a coin, thresholds it, binarizes it, and finds the major and minor axis lengths of the segmented elliptical using the regionprops function. What I want to do is output a subplot where I draw the axes used to calculate the 'MajorAxisLength' and 'MinorAxisLength' over the original image. Would really appreciate help with this.
I have appended the code for your perusal.
rgbImage = imread(coin2.jpg);
subplot(2, 3, 1);
imshow(rgbImage, []);
title('Original Image');
redChannel = rgbImage(:, :, 1);
binaryImage = redChannel < 100;
subplot(2, 3, 3);
imshow(binaryImage, []);
title('Binarized Image');
labeledImage = bwlabel(binaryImage);
area_measurements = regionprops(labeledImage,'Area');
allAreas = [area_measurements.Area];
biggestBlobIndex = find(allAreas == max(allAreas));
keeperBlobsImage = ismember(labeledImage, biggestBlobIndex);
measurements = regionprops(keeperBlobsImage,'MajorAxisLength','MinorAxisLength')
% Display the original color image with outline.
subplot(2, 3, 4);
imshow(rgbImage);
hold on;
title('Original Color Image with Outline', 'FontSize',fontSize);
boundaries = bwboundaries(keeperBlobsImage);
blobBoundary = boundaries{1};
plot(blobBoundary(:,2), blobBoundary(:,1), 'g-', 'LineWidth', 1);
hold off;
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Respuesta aceptada
Rick Rosson
el 3 de Abr. de 2012
Here's a start:
ctr = regionprops(keeperBlobsImage,'centroid');
theta = regionprops(keeperBlobsImage,'orientation');
xMajor = ctr(1) + [ -1 +1 ] * measurements(1)*cosd(theta)/2;
yMajor = ctr(2) + [ -1 +1 ] * measurements(1)*sind(theta)/2;
line(xMajor,yMajor);
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DGM
el 3 de Jun. de 2024
% a logical image with multiple blobs
mask = imread('tiltellipses.png')>128;
imshow(mask); hold on
% get the properties of all blobs
S = regionprops(mask,'centroid','orientation','MajorAxisLength','MinorAxisLength');
% annotate each blob
for k = 1:numel(S)
% major
xj = S(k).Centroid(1) + [-1 1] * S(k).MajorAxisLength*cosd(S(k).Orientation)/2;
yj = S(k).Centroid(2) - [-1 1] * S(k).MajorAxisLength*sind(S(k).Orientation)/2;
% minor
xn = S(k).Centroid(1) + [-1 1] * S(k).MinorAxisLength*cosd(S(k).Orientation + 90)/2;
yn = S(k).Centroid(2) - [-1 1] * S(k).MinorAxisLength*sind(S(k).Orientation + 90)/2;
% each pair of lines is one object
plot([xj NaN xn],[yj NaN yn],'-o','linewidth',2)
end
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Image Analyst
el 3 de Jun. de 2024
This is discussed in this blog entry of Steve Eddins:
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