Patent ID: 7181084

Claim:
A device that receives and processes an image signal for sub-band decomposition of an image, the device comprising: a first median filter that receives the image signal and processes signal values of pixel locations (x 0 , y 0 ), (x 0 +1, y 0 ), (x+1, y 0 ), (x 0 , y 0 −1) and (x 0 , y 0 +1) of the image signal to provide a first median filter output signal; a second median filter that receives the first median filter output signal and processes signal values at pixel locations (x 0 , y 0 ), (x 0 −2, y 0 ), (x 0 +2, y 0 ), (x 0 , y 0 −2) and (x 0 , y 0 +2) of the first median output signal to provide a second median filter output signal; a third median filter that receives the second median filter output signal and processes signal values at pixel locations (x 0 , y 0 ), (x 0 −3, y 0 ), (x 0 +3, y 0 ), (x 0 , y 0 −3) and (x 0 , y 0 +3) of the second median filter output signal to provide a third median filter output signal; a first subtractor that computes the difference between the image signal and the first median filter output signal to provide a first sub-band signal; a second subtractor that computes the difference between the first median filter output signal and the second median filter output signal to provide a second sub-band signal; and a third subtractor that computes the difference between the second median filter output signal and the third median filter output signal to provide a third sub-band signal; where each of the median filters considers not only the signal value at the pixel location (x 0 ,y 0 ) but also the signal values of four other pixels (x 0 k,y 0 ), (x 0 −k,y 0 ), (x 0 ,y 0 +k), and (x 0 ,y 0 −k) which, in a cruciform arrangement, are at the same distance from pixel (x 0 ,y 0 ) in the horizontal and the vertical direction.