Finding the "center" of an extended ring
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I have been experimenting with the image processing toolbox's function "imfindcircles", and it works well. However, there is one issue: I have an extended big ring in the image where I want to recognise its "center" instead of the outer end of the ring (see attached figure, where the outer end is plotted with viscircles and the center and radius found by imfindcircles).
This is also mirrored in the data itself: both the inner and outer end of the big ring have a lower intensity than its center. Is there a way to force "imfindcircles" to use the ring of maximum intensity? (Note that I have applied a thresholding to my image, otherwise the gradient at the ring ends would not be as harsh, and imfindcircles would struggle to differentiate between the ring and artifacts neighbouring the ring.)
Or is there maybe an alternative that includes a second step? After all, the circle center is properly recognised, so I can maybe vary the radius slightly? Maybe I could add up all the values of pixels that would lie on the circle, and see where that reaches its maximum. Is there an easy way to do something like that?
openfig findcircle-test.fig
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Matt J
2024-8-13,1:23
编辑:Matt J
2024-8-13,1:33
load Image
BW0=BW;
A=bwareafilt( imfill(BW,'holes'),1);
BW=imclose(A.*BW, strel('disk',3));
B=bwconvhull(~(~A|BW));
midline=bwskel(BW&~B); %midline of annulus
imshow(BW0+midline,[])
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Matt J
2024-8-13,13:58
Yes, you can use circularFit() from this FEX download,
[y,x]=find(midline);
cfit=circularFit([x,y]')
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