Help to find ellipse in a image, with a known centre

Question

Magnus on 16 May 2015

1
Link

Direct link to this question

https://www.mathworks.com/matlabcentral/answers/217079-help-to-find-ellipse-in-a-image-with-a-known-centre

Commented: Image Analyst on 17 May 2015

Hi, I'm new to image processing, and haven't used matlab for several years.

I'm an orthopedic surgeon and I want to make a program that checks the position of the pelvis-cup, after total hip replacement.

1-The program finds the round metallic caput (head) on the proximal part of the femur-component and marks the center

2- I want to find the long and short axis of the ellipse in the picture.

Manually I can rotate the picture and use

% imellipse

I know the center I found in 1, is a point in the middle of the two foci in the ellipse "they share the same center"

Can someone help me?

1 Comment
Show -1 older commentsHide -1 older comments

Magnus on 17 May 2015

I need help to get from picture 2 to picture 3. This is my code

    gray_image = rgb2gray(img);
    imshow(img);
 %Exeter
    [centers, radii] = imfindcircles(gray_image,[30 60],'Sensitivity',0.92);
 %corail Trilogy
   %[centers, radii] = imfindcircles(gray_image,[40 60],'Sensitivity',0.97);
   cutImg = img(centers(2)-1.5*radii:centers(2)+1.5*radii,centers(1)-1.5*radii:centers(1)+1.5*radii);
    imshow(cutImg)
    hold on
    plot(size(cutImg,1)/2, size(cutImg,2)/2,'r+','MarkerSize',20)
    h = imellipse;
    position = wait(h);