Median centred difference gradient operator and its application in watershed segmentation

A new gradient operator for greyscale images is proposed, the output of which is based on the median centred difference of the intensities within a local mask. The operator is a simplified form of the robust colour morphological gradient and, as such, is robust to impulsive noise and provides well-localised gradient estimates. A quantitative evaluation using simulated images shows that the new operator is particularly suitable for the watershed transform, producing significantly better watershed segmentation results than conventional edge operators such as the morphological gradient and the Sobel.