A method and a system for separating an image signal into a set of image
planes. The system comprises a min-max module, a dynamic threshold module
and a separation module. The min-max module receives the image signal,
searches for a minimum and maximum within at least one window centered on
a current pixel in the image signal. The dynamic threshold module
computes, for the window, based on the respective minimum and maximum
received from the min-max module and the current pixel, a respective
indicator representing the distance and direction of the current pixel
relative to a respective threshold plane, and outputs a control signal
based on the indicator. The separation module separates the image signal
into the set of image planes in accordance with the control signal by
including a representation of the current pixel in at least one of the
image planes.