How to fill a dip at the edge of a binary image

Hi All, I am trying to fill the following binary image to make it into a circle (not a perfect circle though, so trying to make into a circle using the centroid and max diameter provides results which are off a bit). The fact that it is at the edge of the binary object makes it challenging. Any pointers would be extremely useful. Thanks!

Answer 1

[Image Analyst]

Not challenging at all since there's a function in the Image Processing Toolbox that will do that. Get the binary image, then call bwconvhull().

[Mathew Thomas]

Thanks IA, I overlooked this function. It does exactly what I need.