For a light source emits parallel light rays, which gives approximately constant background light intensity, the dark regions can be extracted by setting up value below the intensities of the backgrounds Jiang, C., & Ward, M. O. (1992).
For a light source emits parallel light rays, which gives approximately constant background light intensity, the dark regions can be extracted by setting up value below the intensities of the backgrounds. A technique called "Scanline" is used for this example approach for adaptive threshold chosen Jiang, C., & Ward, M. O. (1992).