How to detect the 6 circles and the center points?

Question

Husain Signalwala 2022-11-10

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1847848-how-to-detect-the-6-circles-and-the-center-points

评论： Husain Signalwala 2022-11-14

I = imread("myimage.jpg"); %original file
imshow(I)
imhist(I)
I = im2gray(I); %coverting to grayscale
Ia = imadjust(I); %histogram stretching
imshow(Ia)
imhist(Ia)
avg = fspecial("average",[50 50]) %average filtering
Iavg = imfilter(Ia,avg);
If = medfilt2(Iavg,[60 60]); %median filtering
imshow(If)
Ibw = imbinarize(If);
imshow(Ibw)
edges = edge(Ibw);
imshow(edges)

From the original image "myimage.jpg" I want to detect the 6 circles and the center point and center line for those cirlces. I tried basic averaging and median filters to make the image smooth and the curves smooth (images attached). After that I tried using hough transform to detect the circles but it did not give me the results.

Is there any function or method that could solve this issue.

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Image Analyst 2022-11-10

I don't see 6 circles. I see a big fuzzy asterisk.

Can you annotate an image and show us exactly where the circles are?

Husain Signalwala 2022-11-11

myimage.jpg

@Image Analyst I want to locate these lines indicated in the figures and the circles(attached). It is not necessary that the centerlines coincide at one point. Any way I can locate these?

Thanks.

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Answer 1

Image Analyst 2022-11-11

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1847848-how-to-detect-the-6-circles-and-the-center-points#answer_1097278

Try using radon

However it's a judgment call as to how far out you want to go to define the boundary of the circle.

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Husain Signalwala 2022-11-11

在 MATLAB Online 中打开

I = imread("myimage.jpg");
imshow(I)
I = im2gray(I);
I = rescale(I);
imshow(I)
I = imadjust(I);
kernel = ones(61);
If = imfilter(double(I),kernel);
imshow(If,[])
BW = edge(If);
imshow(BW)
theta = 0:179;
[R,xp] = radon(BW,theta);
figure
imagesc(theta,xp,R)
colormap("hot")
xlabel("\theta (degrees)")
ylabel("x^{\prime} (pixels from center)")
title("R_{\theta} (x^{\prime})")
colorbar
R_sort = sort(unique(R),"descend");
[row_peak,col_peak] = find(ismember(R,R_sort(1:6)));
xp_peak_offset = xp(row_peak)
theta_peak = theta(col_peak)

@Image Analyst

This is my code until now.

The theta_peak values are [0 2 90 90 90 90], which I think does not give me the solution. Can you just recheck the code? I have applied edges too before applying radon.

I am just a beginner, sorry if there are any dumb mistakes.

Husain Signalwala 2022-11-14

在 MATLAB Online 中打开

@Image Analyst Hello Sir,

By using this code, this is the closest I could come to finding the centerlines. The results are not accurate. From the theta_peak values I had chosen 6 values on assumptions. Can you suggest me something to get a bit more accurate results? Also using radon, all the centerlines meet the centerpoint of the image. This is not true. It is not necessary they all pas through a single point.

I = imread("myimage.jpg");
imshow(I)
I = im2gray(I);
I = rescale(I);
imshow(I)
I = imadjust(I);
BW = edge(I);
imshow(BW)
theta = 0:179;
[R,xp] = radon(BW,theta); %
figure
imagesc(theta,xp,R)
colormap("hot")
xlabel("\theta (degrees)")
ylabel("x^{\prime} (pixels from center)")
title("R_{\theta} (x^{\prime})")
colorbar
R_sort = sort(unique(R),"descend");
[row_peak,col_peak] = find(ismember(R,R_sort(1:12)));
xp_peak_offset = xp(row_peak)
theta_peak = theta(col_peak)
centerX = ceil(size(I,2)/2)
centerY = ceil(size(I,1)/2)
figure
imshow(I)
hold on
scatter(centerX,centerY,50,"bx",LineWidth=2)
axis on
plot(centerX + xp_peak_offset(1,:),tan,"bx",LineWidth=2) %using tan
[x1,y1] = pol2cart(deg2rad(42),600);
plot([centerX-x1 centerX+x1],[centerY+y1 centerY-y1],"r--",LineWidth=2)
plot (961,290,"bx",LineWidth=2)
[x2,y2] = pol2cart(deg2rad(46),500);
plot([centerX-x2 centerX+x2],[centerY+y2 centerY-y2],"r--",LineWidth=2)
[x3,y3] = pol2cart(deg2rad(100),500);
plot([centerX-x3 centerX+x3],[centerY+y3 centerY-y3],"r--",LineWidth=2)
[x4,y4] = pol2cart(deg2rad(106),500);
plot([centerX-x4 centerX+x4],[centerY+y4 centerY-y4],"r--",LineWidth=2)
[x5,y5] = pol2cart(deg2rad(157),500);
plot([centerX-x5 centerX+x5],[centerY+y5 centerY-y5],"r--",LineWidth=2)
[x6,y6] = pol2cart(deg2rad(166),500);
plot([centerX-x6 centerX+x6],[centerY+y6 centerY-y6],"r--",LineWidth=2)