Method and system for improved copy quality in a multifunction reprographic system

• US 20070109602A1
• Filed: 11/17/2005
• Published: 05/17/2007
• Est. Priority Date: 11/17/2005
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Lee, Chia-Hao, Nagarajan, Ramesh, Tse, Francis, Wu, John, Cassidy, John
• Granted Patent: US 7,869,093 B2
• Time in Patent Office: Days
• US Class Current: 358/3.100
• CPC Class Codes: H04N 1/40075 Descreening, i.e. converting a halftone signal into a corresponding continuous-tone signal; Rescreening, i.e. combined descreening and halftoning

Abstract

A method and system reconstructs a contone image from a binary image by first tagging pixels to identify one of a multiplicity of image content types. The tag information and the pattern of bits surrounding the pixel to be converted to a contone value are used to reconstruct a contone image from a binary image. The pattern of bits in the neighborhood is used to generate a unique identifier. The unique identifier is used as the address for a lookup table with the contone value to be used. A filter also generates a contone value. A selector selects between the look-up table contone value and the filter contone value based an image context type.

Claims

1. A system to generate a continuous tone image from tagged binary encoded image, comprising:

a pattern identifier generator to generate a pattern identifier value based upon a pattern of pixels around a pixel of interest;

a filter to generate a filter contone value based upon a neighborhood of pixels around a pixel of interest;

a contone value generator, operatively connected to said pattern identifier generator, to generate a generator contone value from said pattern identifier value; and

a selector, operatively connected to said contone value generator and said filter, to select said filter contone value if the pixel of interest corresponds to pictorial pixels and to select said generator contone value if the pixel of interest corresponds to text pixels.

2. The system as claimed in claim 1, wherein said contone value generator includes a look-up table, said look-up table having a plurality of contone values stored therein, each contone value corresponding to a pattern identifier value.

3. The system as claimed in claim 1, wherein said filter is a two-dimensional filter.

4. The system as claimed in claim 1, wherein said contone value generator includes a memory having a plurality of contone values stored therein, each combination of a pattern identifier value being mapped to a stored contone value.

5. The system as claimed in claim 1, wherein said contone value generator includes a logic circuit to generate a plurality of contone values, the generated contone value corresponding to a pattern identifier value.

6. The system as claimed in claim 1, wherein said contone value generator includes a plurality of look-up tables, each look-up table having a plurality of contone values stored therein, each contone value corresponding to a pattern identifier value.

7. The system as claimed in claim 6, wherein said contone value generator includes an image type selector to generate an image type signal identifying an image context type in a pre-determined neighborhood of pixels around a pixel of interest.

8. The system as claimed in claim 7, wherein said image type signal enables a look-up table associated with the image context type corresponding to said image type signal.

9. A system to generate a continuous tone image from tagged binary encoded image, comprising:

a pattern identifier generator to generate a pattern identifier value based upon a pattern of pixels around a pixel of interest;

a filter circuit to generate a filter contone value based upon a neighborhood of pixels around a pixel of interest;

a contone value generator, operatively connected to said pattern identifier generator, to generate a generator contone value from said pattern identifier value; and

a selector, operatively connected to said contone value generator and said filter, to select said filter contone value if the pixel of interest corresponds to pictorial pixels and to select said generator contone value if the pixel of interest corresponds to text pixels.

10. The system as claimed in claim 9, wherein said filter circuit includes a plurality of filters, each filter generating a different filter contone value, and a selection circuit to output one of the different contone values based upon a type of pictorial pixel of the pixel of interest.

11. The system as claimed in claim 10, wherein said filters are two-dimensional filters.

12. The system as claimed in claim 9, wherein said contone value generator includes a look-up table, said look-up table having a plurality of contone values stored therein, each contone value corresponding to a pattern identifier value.

13. The system as claimed in claim 9, wherein said contone value generator includes a memory having a plurality of contone values stored therein, each combination of a pattern identifier value being mapped to a stored contone value.

14. The system as claimed in claim 9, wherein said contone value generator includes a logic circuit to generate a plurality of contone values, the generated contone value corresponding to a pattern identifier value.

15. The system as claimed in claim 9, wherein said contone value generator includes a plurality of look-up tables, each look-up table having a plurality of contone values stored therein, each contone value corresponding to a pattern identifier value.

16. The system as claimed in claim 15, wherein said contone value generator includes an image type selector to generate an image type signal identifying an image context type in a pre-determined neighborhood of pixels around a pixel of interest.

17. The system as claimed in claim 16, wherein said image type signal enables a look-up table associated with the image context type corresponding to said image type signal.

18. A method to generate a continuous tone image from tagged binary encoded image, comprising:

generating a pattern identifier value based upon a pattern of pixels around a pixel of interest;

filtering a neighborhood of pixels around a pixel of interest to generate a filter contone value;

generating a generator contone value from the pattern identifier value;

selecting the filter contone value if the pixel of interest corresponds to pictorial pixels; and

selecting the generator contone value if the pixel of interest corresponds to text pixels.

19. The method as claimed in claim 18, wherein the filter contone value is generated by a two-dimensional filter.

20. The method as claimed in claim 18, wherein the filter contone value is generated by one of a plurality of two-dimensional filters.