Given a numeric vector with the pixel's intensities, returns the threshold value based on Otsu's method, which minimizes the combined intra-class variance
References
Otsu, N. 1979. Threshold selection method from gray-level histograms. IEEE Trans Syst Man Cybern SMC-9(1): 62–66. doi: doi:10.1109/tsmc.1979.4310076
Examples
img <- image_pliman("soybean_touch.jpg")
thresh <- otsu(img@.Data[,,3])
plot(img[,,3] < thresh)
