Halftoning implementation for interactive image editing

• US 4,706,077 A
• Filed: 09/08/1981
• Issued: 11/10/1987
• Est. Priority Date: 09/08/1981
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Sangster, Andrew, Stroll, Zoltan, Roberts, Allen M.
• Primary Examiner(s): Curtis, Marshall M.
• Application Number:
  US06/300,349
• Time in Patent Office: 2,254 Days
• Field of Search: 358/283, 358/280, 358/284, 358/138, 358/133, 340/728, 340/793
• US Class Current: 345/599
• CPC Class Codes: H04N 1/4051 producing a dispersed dots halftone pattern, the dots having substantially the same size different sizes H04N1/4057
• CPC Class Codes: H04N 1/4055 producing a clustered dots or a size modulated halftone pattern

Abstract

A circuit for producing a "knight ordered dither" halftone 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.

Claims

1. 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.

2. 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.

3. The method of assigning threshold values to each element of a three by three element halftone matrix comprising the steps of:

determining a set of nine numerically ascending or descending threshold values, and

assigning these values to said matrix in a knight tour pattern.

4. 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.

5. 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.

6. A three by three element halftone matrix comprising:

a set of nine numerically ascending or descending threshold values, the elements of said matrix numbered, row by row, as follows;

6, 9,4,3,1,7,8,5,2, said set of threshold values assigned to said matrix in numerical order.

7. A six by six element halftone matrix comprising a set of 36 numerically ascending or descending values, the elements of said matrix numbered, 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, and 6, said set of threshold values assigned to said matrix in numerical order.

8. A three by three element halftone matrix comprising numerically ascending or descending threshold values assigned to said matrix in a knight tour pattern.

9. A six by six element halftone matrix comprising a set of thirty-six numerically ascending or descending threshold values assigned to said matrix in a knight ordered dither pattern.

10. A nine by nine element halftone matrix comprising a set of eighty-one numerically ascending or descending threshold values, assigned to said matrix in a two level nested knight tour pattern.