The algorithm calculates the mean value in a window and if the pixel's intensity is above the mean the pixel is set to white colour, otherwise the pixel is set to black colour. To increase the resistance to noise the threshold value can be shifted by a constant c. The pseudocode:
if (pixel >= mean-c)
pixel = 1;
pixel = 0;
Jan Motl (2020). Meanthresh local image thresholding (https://www.mathworks.com/matlabcentral/fileexchange/41787-meanthresh-local-image-thresholding), MATLAB Central File Exchange. Retrieved .