How to saperate these overlapping objects ?

I want to detect concave points of overlapping objects so that I can fit a circle and an ellipse or combination of 2 circles over it.

[KALYAN ACHARJYA]

Can you elaborate more with the color symbol indicated by marker?

You can use paint?

[Namrata Patil]

I want to place green circle over circular objects and an ellipse over elliptical objects. But as some objects are overlapping I have to seperate them first by detecting their intersecting points.

Answer 1

[Image Analyst]

Why not just use regionprops to look for blobs that have high solidity?

mask = imfill(mask, 'holes');
props = regionprops(mask, 'Solidity', 'MajorAxisLength', 'MinorAxisLength');
allSolidities = [props.Solidity]
allMajorAxesLengths = [props.MajorAxisLength]
allMinorAxesLengths = [props.MinorAxisLength]
nonConvexIndexes = allSolidities < 0.8; % or whatever.
circleIndexes = (allMajorAxesLengths ./ allMinorAxesLengths) < 1.5; % Or whatever.

Circles should have minor and major axes roughly the same.

Adapt as needed.

Answer 2

[Image Analyst]

See Steve's blog: http://blogs.mathworks.com/steve/2010/07/30/visualizing-regionprops-ellipse-measurements/

[Namrata Patil]

Thanks for helping. I am facing same error as Steve's code . Ellipse of same size doesn't fit if two cells are overlapped. For that I have to saperate them first.