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Method of smoothing image signals

  • US 4,827,533 A
  • Filed: 03/17/1987
  • Issued: 05/02/1989
  • Est. Priority Date: 03/17/1986
  • Status: Expired due to Term
First Claim
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1. A method of smoothing image signals that combine to define an image comprising a plurality of picture elements each element being represented by an image signal, which comprise the steps of:

  • (i) designating an original image signal at a picture element P of a two-dimensional image by a signal value X, designating image signals at a picture elements Pa and Pc adjacent to said picture element P in a longitudinal direction and image signals at picture elements Pb and Pd adjacent to said picture element P in a transverse direction respectively by signal values a, c, b and d, and designating positive constants by α and

    β

    .(ii) processing said image signals to yield a transformed original image signal C'"'"' by(a) transforming said original image signal X into a transformed image signal having a signal value X'"'"' which is a median value of said original image signal X, (a+α

    ), (a-α

    ), (b+β

    ) and (b-β

    ) calculated when an absolute value of a different between the values of said image signals a and b is smaller than a predetermined value Q, and(b) smoothing said original image signal X based on values of said image signals a and b and said transformed image signal value X'"'"' when the absolute value of the difference between the values of said image signals a and b is not smaller than the predetermined value Q, said processing being conducted sequentially for the respective original image signals in a predetermined order, wherein a and b denote the transformed signals obtained by conducting said processing for the original image signals at said picture elements Pa and Pb adjacent to said picture element P,(iii) processing said original image signal X into a transformed image signal having a value by(a) calculating X" a median value of said original image signal X, (c+α

    ), (c-α

    ), (d+β

    ) and (d-β

    ) when an absolute value of a difference between said image signals c and d is smaller than the predetermined value Q, and(b) smoothing said original image said X based on values of said image signals c and d and said transformed image signal value X" when the absolute value of the difference between said image signals c and d is not smaller than the predetermined value Q, said processing being conducted sequentially for the respective original image signals in an order reverse to said predetermined order, wherein c and d denote the transformed signals obtained by conducting said processing for the original image signals at said picture elements Pc and Pd adjacent to said picture element P, and(iv) calculating a mean value of said transformed signal X'"'"' and said transformed signals X" at the same picture element, and using the mean values thus obtained as smoothed signals at the respective picture elements.

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