Image analysis – Image compression or coding – Adaptive coding
Patent
1995-09-20
1999-06-29
Au, Amelia
Image analysis
Image compression or coding
Adaptive coding
358429, 358457, G06K 936, G06K 946
Patent
active
059179520
ABSTRACT:
A bi-level dithered image is compressed using knowledge of the particular dither matrix used to generate the dithered image from an original high resolution grey-scale image. A lower resolution grey-scale image is substituted for the original high resolution grey-scale image (which may be further compressed with known compression techniques), such that after the two images (after any required decompression) have been dithered by that same dither matrix, the resultant dithered images are the same (lossless compression) or substantially the same (lossy compression). In a preferred embodiment, the lower resolution encoded multi-tone image is based on variable sized blocks of pixels, with the dither matrix being used to determine an optimal size and intensity of each block in the encoded image such that when the lower resolution image is dithered, it is indistinguishable from the dithered original image. Since the encoded image is in effect merely a lower resolution version of the original image with the "blue" noise introduced by the dithering process removed, it can be further compressed by a conventional compression algorithm (such as the "JPEG" algorithm for lossy compression of continuous tone images or the "Ziv/Lempel" algorithm for lossless compression of digital data).
REFERENCES:
patent: 3562420 (1971-02-01), Thompson
patent: 5243446 (1993-09-01), Pollich et al.
patent: 5430555 (1995-07-01), Sawada et al.
patent: 5463703 (1995-10-01), Lin
patent: 5506624 (1996-04-01), Moreton
Au Amelia
Hewlett--Packard Company
Johnson Timothy M.
Potts Jerry R.
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