Color digital halftoning with vector error diffusion

DETAILED DESCRIPTION We claim: 1.
A method of producing a halftone digital color image having pixels representing values in an output color space from a continuous tone color digital image having pixels representing continuous values in an input color space, comprising the steps of: a.
transforming a pixel in the input color space to a vector in a preferred color space; b.
representing all possible values in the output color space as output vectors in the preferred color space; c.
selecting and output vector in the preferred color space that is closest to the transformed input pixel; d.
calculating an error vector in the preferred color space as the distance between the transformed input pixel and the selected output vector; e.
distributing by weighted addition the calculated error vector to a neighborhood of adjacent input pixels to be processed; and f.
translating the selected output vector to a pixel in the output color space.
2.
The method claimed in claim 1, wherein the preferred color space is a uniform visual color space.
3.
The method claimed in claim 2, wherein the preferred color space is CIELUV.
4.
The method claimed in claim 1, further comprising: employing a neighborhood of previously selected output vectors weighted by a human visual system blur filter to produce a blurred output vector and using the blurred output vector as the output vector employed in the error determining step.
5.
The method claimed in claim 4, wherein the neighborhood is a previously calculated portion of an array of pixels, and said human visual system filter is a digital filter having the weights:
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Description



Description:
CROSS REFERENCE TO RELATED APPLICATION Reference is hereby made to copending U.
S.
patent application Ser