Method of encoding high resolution edge position information in continuous tone image information

Claim 2

In a printing system, receiving document images including both text/line art regions, and pictorial regions, a method for optimizing tonal and edge rendition including: receiving text/line art regions of the document image as binary pixels at a text/line art frequency selected to avoid aliasing effects at any edge pixels therein; receiving pictorial regions of the document image as continuous tone pixels, at a frequency lower than said text/line art frequency; applying an anti-aliasing filter to said text/line art regions, to replace some edge pixels with gray level pixels having a first number of levels M; converting said document image to a binary representation thereof; converting each of said M levels in said text/line art regions to a binary representation reflecting correct edge position of said text/line art regions; and converting said contone pixels to a binary representation determined by a halftone pattern having N levels selected for said contone pixels, whereby information about the presence of text/line art regions and pictorial regions is passed without a tag bit.

Claim 3

The method as described in claim 1 where N is much larger than M.

Claim 4

The method as described in claim 1, wherein for a system using L bits of information, M+N=2 L .

Claim 5

The method as described in claim 1, wherein, prior to said converting step, said continuous tone pixels are tone corrected, to account for a particular system, said tone correction outputting N output levels.

Claim 6

In a printing system, receiving document images including both text/line art regions, and pictorial regions, a method for optimizing tonal and edge rendition, and carrying optimizing information with the document image, comprising: receiving text/line art regions of the document image as binary pixels at a text/line art frequency selected to avoid aliasing effects at any edge pixels therein; receiving pictorial regions of the document image as continuous tone pixels, at a frequency lower than said text/line art frequency; applying an anti-aliasing filter to said text/line art regions, to replace some edge pixels therein with gray level pixels having a first number of levels M selected to optimally reproduce said edge pixels; converting said document image including continuous tone pixels and gray level pixels to a binary representation thereof using one of L possible binary patterns, including M patterns representing binary edge placement patterns and N patterns representing binary gray reproduction patterns, including: converting each of said M levels, in said text/line art regions to a binary representation selected from said M patterns reflecting correct edge position of said text/line art regions; and converting said contone pixels to one of said N binary representation determined by a halftone pattern having N levels selected for said contone pixels.

Claim 7

In a printing system, receiving document images including both text/line art regions, and pictorial regions, a method for optimizing tonal and edge rendition, and carrying optimizing information with the document image, comprising: receiving text/line art regions of the document image as binary pixels at a text/line art frequency selected to avoid aliasing effects at any edge pixels therein; receiving pictorial regions of the document image as continuous tone pixels, at a frequency lower than said text/line art frequency; applying an anti-aliasing filter to said text/line art regions, to replace some edge pixels therein with gray level pixels having a first number of levels M selected to optimally reproduce said edge pixels; converting said document image including continuous tone pixels and gray level pixels to a binary representation thereof using one of L possible binary patterns, including M patterns representing binary edge placement patterns and N patterns representing binary gray reproduction patterns, including: converting each of said M levels, in said text/line art regions to a binary representation selected from said M patterns reflecting correct edge position of said text/line art regions; and converting said contone pixels to one of said N binary representation determined by a halftone pattern having N levels selected for said contone pixels.

Claim 8

The method as described in claim 5, where N is much larger than M.

Claim 9

The method as described in claim 5, wherein M+N=2 L .

Claim 10

The method as described in claim 5, wherein, prior to said converting step, said continuous tone pixels are tone corrected, to account for a particular system, said tone correction outputting N output levels.