Image Segmentation
SEGMENTATION USING BOUNDARY CHARACTERISTICS
The number of pixels covered by objects to be segmented is almost always a very small portion of the total number of pixels in the image: the histogram is then almost unimodal.
The histogram may be made closer to being bimodal if only pixels on or near the boundaries of object regions are considered.
Such a selection of pixels may be achieved by using gradient and Laplacian operators:
where G(x, y) is a gradient, L(x, y) is the Laplacian,
T is a threshold; 0, +, - represent three distinct gray levels.