An experimental design approach to image enhancement

An experimental design approach that treats the gray-level value of each pixel as an observation is proposed. Any pixel corrupted by salt-and-pepper noise is considered to be a missing observation. An estimate of a missing observation is derived using a 5×5×5×5 Graeco-Latin squares experimental design model fitted to a 5-pixel×5-pixel mask. Edge-preserving smoothing of images corrupted by a mixture of Gaussian and salt-and-pepper noise is carried out in two steps. First a 5×5×5×5 Graeco-Latin squares mask is used to determine the presence of horizontal, vertical, 45° diagonal, or 135° diagonal edges and localize them using analysis of variance (ANOVA) on contrasts. The center pixel in the 5-pixel×5-pixel mask is then replaced by the average of all the pixels on the same side of the edge that includes the center pixel. The process is powerful and efficient. The uniformly most powerful property of the ANOVA methodology in the presence of Gaussian noise ensures the optimum suppression of the Gaussian noise background