EP0074794A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Apparatus and method for producing halftone patterns
Assignee: Xerox Corp
•
Filing: 1982-09-08
•
Granted: —
•
Expires: 2002-09-08
Abstract
Abstract A circuit for producing a "knight ordered dither" half- . tone pattern for a CRT and a "double spiral" halftone pattern for a xerographic printer is described. The circuit comprises a RAM for storing the threshold values, a comparator, and supporting addressing and logic parts. Also described are a program for allowing the operator to interactively generate threshold patterns, and several knight tour patterns specifically designed for a CRT using interlaced rasters.
Inventors
- 👤 Allen M. Roberts
- 👤 Andrew Sangster
- 👤 Zolton Stroll
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-28 12:30
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/405; H04N1/4055; H04N1/4051
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
113 words
Apparatus for producing halftone threshold values comprising: an m by m word random access memory (RAM), (73, 74) of n bits per word, for temporarily storing threshold values, two modulo y counters (71, 72) for supplying the address information to said RAM, the first counter for sequentially addressing the locations in RAM containing the threshold values along any matrix row, the second counter incrementing at the end of each line to provide a change of row values from one matrix line to the next, and a comparator (75, 76) for comparing each n bit gray scale pixel to each threshold value to produce a binary output bit for each input gray scale input.
Claim 2
Dependent Claim
113 words
Apparatus for producing halftone threshold values comprising: an m by m word random access memory (RAM), (73, 74) of n bits per word, for temporarily storing threshold values, two modulo y counters (71, 72) for supplying the address information to said RAM, the first counter for sequentially addressing the locations in RAM containing the threshold values along any matrix row, the second counter incrementing at the end of each line to provide a change of row values from one matrix line to the next, and a comparator (75, 76) for comparing each n bit gray scale pixel to each threshold value to produce a binary output bit for each input gray scale input.
Claim 3
Dependent Claim
41 words
The apparatus of claim 1, further comprising control means for enabling said system to produce a plurality of halftone patterns, said control means comprising: means for varying y, and means for loading said RAM with a different set of threshold values.
Claim 4
Dependent Claim
27 words
The apparatus of claim 2, wherein said control means is a computer for recomputing said threshold values under interactive operator control to vary the tonal rendition curve.
Claim 5
Independent Claim
115 words
A method of producing a halftone pattern, comprising the steps of: loading into the first y rows of the first y columns of an m by m word random access memory (RAM) (73, 74) the threshold values of a y row by y column halftone matrix, using a first modulo y counter (71) to address said RAM to increment through each row to output one threshold value for each input gray scale pixel received, using a second modulo y counter to change the addressing from one row to the next at the end of each line, and comparing each gray scale pixel to the associated threshold level to produce a series of binary bit outputs.
Claim 6
Independent Claim
115 words
A method of producing a halftone pattern, comprising the steps of: loading into the first y rows of the first y columns of an m by m word random access memory (RAM) (73, 74) the threshold values of a y row by y column halftone matrix, using a first modulo y counter (71) to address said RAM to increment through each row to output one threshold value for each input gray scale pixel received, using a second modulo y counter to change the addressing from one row to the next at the end of each line, and comparing each gray scale pixel to the associated threshold level to produce a series of binary bit outputs.
Claim 7
Dependent Claim
32 words
The method of Claim 4 further comprising the steps of: changing the value of y, and loading a different set of threshold values into said RAM to produce a different halftone pattern.
Claim 8
Dependent Claim
29 words
The method of Claim 5 further comprising the step of interactively varying the tonal rendition curve by recomputing and then loading into said RAM another set of threshold values.
Claim 9
Independent Claim
65 words
The method of assigning threshold values to each element of a 3 by 3 element halftone matrix comprising the steps of: determining a set of nine numerically ascending or descending threshold values, numbering the elements of said matrix, row by row, as follows: 6, 9, 4, 3, 1, 7, 8, 5, 2, and assigning said set of threshold values to said matrix in numerical order.
Claim 10
Independent Claim
65 words
The method of assigning threshold values to each element of a 3 by 3 element halftone matrix comprising the steps of: determining a set of nine numerically ascending or descending threshold values, numbering the elements of said matrix, row by row, as follows: 6, 9, 4, 3, 1, 7, 8, 5, 2, and assigning said set of threshold values to said matrix in numerical order.
Claim 11
Independent Claim
114 words
The method of assigning threshold values to each element of a 6 by 6 element halftone matrix comprising the steps of: determining a set of 36 numerically ascending or descending threshold values, numbering the elements of said matrix, row by row, as follows: 21, 33, 13, 23, 35,15, 9, 1, 25, 11, 3, 27, 29, 17, 5, 31, 19, 7, 24, 36, 16, 22, 34, 14, 12, 4, 28, 10, 2, 26, 32, 20, 8, 30, 18, 6 and assigning said set of threshold values to said matrix in numerical order. determining a set of nine numerically ascending or descending threshold values, and assigning these values to said matrix in a knight tour pattern.
Claim 12
Independent Claim
114 words
The method of assigning threshold values to each element of a 6 by 6 element halftone matrix comprising the steps of: determining a set of 36 numerically ascending or descending threshold values, numbering the elements of said matrix, row by row, as follows: 21, 33, 13, 23, 35,15, 9, 1, 25, 11, 3, 27, 29, 17, 5, 31, 19, 7, 24, 36, 16, 22, 34, 14, 12, 4, 28, 10, 2, 26, 32, 20, 8, 30, 18, 6 and assigning said set of threshold values to said matrix in numerical order. determining a set of nine numerically ascending or descending threshold values, and assigning these values to said matrix in a knight tour pattern.
Claim 13
Independent Claim
45 words
The method of assigning threshold values to each element of a six by six element halftone matrix comprising the steps of: determining a set of thirty-six numerically ascending or descending threshold values, and assigning these values to said matrix in a knight ordered dither pattern.
Claim 14
Independent Claim
45 words
The method of assigning threshold values to each element of a six by six element halftone matrix comprising the steps of: determining a set of thirty-six numerically ascending or descending threshold values, and assigning these values to said matrix in a knight ordered dither pattern.
Claim 15
Independent Claim
47 words
The method of assigning threshold values to each element of a nine by nine element halftone matrix comprising the steps of: determining a set of eighty-one numerically ascending or descending threshold values, and assigning these values to said matrix in a two level nested knight tour pattern.
Claim 16
Independent Claim
47 words
The method of assigning threshold values to each element of a nine by nine element halftone matrix comprising the steps of: determining a set of eighty-one numerically ascending or descending threshold values, and assigning these values to said matrix in a two level nested knight tour pattern.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.