Image analysis – Image compression or coding – Quantization
Patent
1997-05-23
1999-04-06
Rogers, Scott
Image analysis
Image compression or coding
Quantization
382237, 382270, 382304, 358456, 358466, H04N 1405
Patent
active
058928510
ABSTRACT:
A process and apparatus is described to improve error diffusion halftone imaging by reducing the amount of time necessary to perform the halftoning process. This processing time reduction is produced without sacrificing the quality of the output binary images by achieving parallelism of error diffusion within an image row. The method works by cutting each image row into a number of segments and error diffusing these segments in parallel. It utilizes two different error diffusion filters: the cut filter for the pixel just before the cuts and the normal filter for the rest of the pixels. Dependencies among the segments is eliminated by ensuring that the cut filter has zero weight for the right neighboring pixel. The normal filter can be any filters that can show excellent quality of the output binary images. Banding artifacts along the cuts are minimized through careful design of the cut filter. The artifacts can also be subdued by using different positions of the cuts for different image rows, by using different cut filters for different rows, or by adding noise to the two pixels on both sides of the cuts. Alternately, a cut filter is employed that can eliminate the banding effects completely, in the majority of cases. In this design, many possible filters are evaluated and the best ones are chosen systematically. Furthermore, in the new method, the data are within an image row, and hence can be quickly rearranged to a form that will speed up parallel processing in a Single Instruction Multiple Data architecture such as the Intel MMX architecture.
REFERENCES:
patent: 5604605 (1997-02-01), Moolenaar
Hewlett--Packard Company
Rogers Scott
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