Dither method and printing apparatus
US6111658A · kind A · utility
Assignees
Inventor
Key dates
| Filing date | Dec 8, 1997 |
| Grant date | Aug 29, 2000 |
| Priority date | — |
| Expiry date | Dec 8, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K2215/0094
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A ROM in the control circuit of a color printer stores a threshold matrix. The individual elements of the threshold matrix correspond to print dots, the number of which is X.times.Y and which form 1 pixel in the original image. Values t (x, y) which are integral numbers not less than 0 are assigned one to each of the individual elements in a predetermined order. Using the threshold matrix, the CPU of the control circuit creates mask patterns for representing halftones. A value of 1 is subtracted from the tone number allotted to the tone of color of a pixel in an image to be printed, and the resultant value is substituted for a variable G. When a gradation for image data representing the pixel is given as "g", the condition required for setting ON (transferring toner to print) the dot specified by the coordinates (x, y) in the pixel in the case of the gradation "g" is expressed by the following formula (6): EQU t (x, y).ltoreq.g.times.X.times.Y/G (6) Based on the threshold matrix and the formula (6), the CPU of the control section creates mask patterns in the case where the gradation "g" takes values 0 to G-1 in sequence, and develops those mask patterns in a RAM.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.