Method and apparatus for spatially variant filtering

Details Method and apparatus for spatially variant filtering Method and apparatus for spatially variant filtering

1993-03-09

1996-01-02

Boudreau, Leo H.

Image analysis

Image enhancement or restoration

Image filter

382263, 382272, G06K 940

Patent

active

054816289

ABSTRACT:
An adaptive spatial filter for digital image processing selectively performs spatial high pass filtering of an input digital signal to produce an output pixel value having an enhanced signal level using a gain factor that effects a variable degree of enhancement of the input pixel, so that pixels whose activity values are close to an iteratively adjustable activity threshold level will be emphasized significantly less than pixels whose associated activity values are substantially above the threshold level. The activity threshold level is selectively updated at the end of a scan line in accordance with prescribed spatial activity criteria, so as to effectively prevent discontinuities in the threshold level during line-by-line adjustment and to take into account how `noisy` the background is. Potential corruption of the updated value of a pixel by an edge portion of the image is avoided by requiring that pixels which are associated with background or signal regions of the image be respectively less than or greater than a local mean value. Otherwise the pixel values are not modified.

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patent: 4941190 (1990-07-01), Joyce
patent: 5038388 (1991-08-01), Song
patent: 5081692 (1992-01-01), Kwon
patent: 5231677 (1993-01-01), Mita et al.

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