This method assumes that each bubble includes one
major white spot caused by illumination. Each white spot
represents each bubble. Therefore, the number of bubbles
in a froth image can be estimated by the white spot
distribution. Statistically, the white spot size is
proportional to the bubble size, and inversely
proportional to average bubble size. A dynamic optimal
thresholding technique is used to detect and extract white
spots in the froth image[12].