Image smoothing based on pixel grouping

In this paper we describe an image smoothing method that is capable of reducing both Gaussian noise and impulse noise. For each pixel in an image we examine a window area that is centered at the pixel. Pixels within the window are then divided into three groups based on their intensities relative to the center pixel. One group has higher intensities. One group has lower, and the third group has intensities close to that of the center pixel. A new intensity value for the center pixel is then determined by averaging the pixels in one or more groups based on the population of the three groups. Therefore, the number of pixels used in averaging and the configuration of these pixels may vary from point to point. This high adaptability enables the approach to preserve the sharpness of edges, corners, lines, and other image features in the smoothing process.