How to find gray point?

1

Up to now I could not find a way to find the center of the dark-grey spot in the image. What is the best way to find the center point?

test
test251×253 35.9 KB

Thanks

2

crosspost:

3

You need to provide your attempts that didn’t work lest to waste readers’ time.
For instance, have you tried the obvious thing: 1) subtract background (the way to subtract it, though, must be the one suggested in J.Chen, C.S.Brooks “Experimental and CFD simulation of mass transfer and hydrodynamics in a cylindrical bubble column”, Chem.Eng.Sc., 2021, namely, invert the image and the background, subtract them and invert the result, otherwise background subtraction wouldn’t work because your dot is a dark spot on a bright background), 2) apply a simple intensity threshold, 3) find the external contour, 4) find the center of the external contour?