What is the algorithm used in the Measurement Plugin to calculate %Area?

Hi, hope you are safe and doing well.

I would like to know what is the algorithm used to calculate the %Area of a segmented image (is it the white pixels over black ones or the inverse?)

Please refer to the source article if possible, I couldn’t find any documentation about it (only the explanation on how to use it, but this is not what I want for now).

Thank you in advance.

It is specified in the imagej user guide: https://imagej.nih.gov/ij/docs/guide/146-30.html#toc-Subsection-30.7

Area fraction For thresholded images is the percentage of pixels in the image or selection that have been highlighted in red using Image▷Adjust▷Threshold… [T]↑. For non-thresholded images is the percentage of non-zero pixels. Uses the heading %Area .