Feature Extraction Using Median Filtering Technique
Chetlur S. Sridhar, G. Devarajan, V.K. Aatre · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1987
Two dimensional Median filtering has been used in picture processing for improved noise performance. Salt and pepper noise and spikes have been successfully removed using median filters. In this work the application of median filtering for finding hidden contours in an image is presented. The principle used is to obtain the correlation of pixels in a line of the image after passage through a median filter of suitable window width and determine the trend changes exhibited by this. Since those samples which show trend changeover are not passed by the median filter the output correlation must indicate changes whenever the part of the image exhibits trend changeover. This is most likely to occur when there are hidden contours in the image. The study also includes comparison of the DFTs of the image lines after passage through the median filter (standard scanning is assumed and the image intensity is available in a digitized form) with the original. This experiment also shows interesting results. It is shown that a theoretical basis can be established for this performance.