Largest enclosed convex shape to measure eggs with appendages

Posted by Tom Kazimiers on
URL: http://imagej.273.s1.nabble.com/Largest-enclosed-convex-shape-to-measure-eggs-with-appendages-tp5004483.html

Dear all,

On images like the one attached, I want to measure the maximum length of
each eggshell. Those eggshells are ellipse like structures with usually
two smaller appendages. Those, however, shouldn't be part of the
measurement, but only the eggshell itself.

Unfortunately, it isn't enough to threshold the image and find the
longest straight line in the egg. The problem is: if the appendages are
inconveniently located, the longest straight line will go through them
as well---which wouldn't be what I want to measure.

Therefore, I thought, it would be best to threshold first and then find
the largest enclosed convex shape and then do the measuring on this
shape. Now, I guess I could implement something like

    A Polynomial Solution For Potato-Peeling And Other Polygon Inclusion
    And Enclosure Problems (J. S. Chang and C. K. Yap 1984),

but I was wondering if there is something similar in ImageJ/Fiji already
that I miss or if you have another suggestion on how to do those
measurements. Any ideas?

I tried to use the watershed plugin and it cut the appendages in most
cases, but not in all. Also the cuts where sometimes rather far away
from the egg itself and so the longest straight line could still go
through the cut appendage.

Thanks in advance,
Tom

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