Is there a way to threshold the background out of the image, to leave only the object?

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Hi folks,
I have images that look like the following, and I'm trying to threshold out the background. For some images, this is a very straightforward endeavour. For others, however, it's not that easy because the background and object have similar greyscale levels.
Ultimately, I want to use regionprops() to measure the object's properties.
May I please ask if there's a way to get around this?
My images look like this:

Accepted Answer

Image Analyst
Image Analyst on 4 Aug 2021
Edited: Image Analyst on 4 Aug 2021
Try imbinarize(). Then check the mean gray level in the center of the mask image and compare it to the mean gray level at the top of the image. If the mask is dark in the center and bright around the top, then invert the mask. Something like (untested)
mask = imbinarize(grayImage);
[rows, columns] = size(mask);
row = round([rows/2-50 : rows/2+50]);
col = round([columns/2-50 : columns/2+50]);
if mean2(mask(1:10)) > mean2(mask(row, col))
% Mask at top is white and in middle is black. Need to invert it.
mask = ~mask;

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