Patent ID: 6226050
Filing Date: 2001-05-01
Classification: H04N

Abstract:
A signal adaptive filtering method for reducing ringing noise in image data, comprising the steps of:(a) calculating a gradient of an image data being filtered at each pixel, using a one-dimensional horizontal gradient operator of 1.times.2 size and a one-dimensional vertical gradient operator of 2.times.1 size, both having a weighted value (1,-1), and comparing the absolute value of the calculated gradient with a predetermined threshold value to generate a binary value,wherein the threshold value of the step (a) is set to a value determined based on a filter window size, if a quantization step Q is greater than the value corresponding to the filter window size, and the threshold value is set equal to Q, if the quantization step Q is less than or equal to the value corresponding to the filter window size;(b) repeating said step (a) on a pixel block having a predetermined size by a pixel unit to generate a binary edge map with respect to a whole block;(c) applying a filter window of the predetermined size to the generated binary edge map to determine whether edges are present in the filter window;(d) filtering the pixel values of the corresponding filter window pixel by pixel by using predetermined first weighted values to generate a new pixel value if it is determined in said step (c) that edges are not present; and(e) filtering the pixel values of the corresponding filter window pixel by pixel by using predetermined second weighted values to generate a new pixel value if it is determined in said step (c) that edges are present, wherein no filtering is performed if the pixel located at the center of the filter window represents an edge.