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CONVERTING BETWEEN WRITE - WHITE, WRITE - BLACK, AND NEUTRAL BITMAPS

IP.com Disclosure Number: IPCOM000026508D
Original Publication Date: 1992-Jun-30
Included in the Prior Art Database: 2004-Apr-06
Document File: 8 page(s) / 406K

Publishing Venue

Xerox Disclosure Journal

Abstract

Two types of electrophotographic systems are well known, a first system, commonly referred to as a write-white or charged area development system, uses a laser to dissipate charge on the photoconductive surface in areas where development or printing is not desired. Thus, it might be said that white pixels are written to the photoconductive surface. In a second system, commonly referred to as a write-black or discharged area development system, the laser dissipates charge on the photoconductive surface in areas where development or printing is desired. Thus, it may be said that black pixels are written to the photoconductive surface. While each system is capable of producing a high quality reproduction. both have a distinct artifact occurring as a result of the imaging process. Write-white systems tend to shrink or erode black lines, while write-black systems tend to expand black lines. The change in line width can lead to the breaking of letters for small fonts in write-white printers, along with the overall appearance of the printed image appearing to be too light. For write-black printers, the result may be a closing of small letters, along with the overall appearance of a printed image appearing too dark.

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Page 1 of 8

XEROX DISCLOSURE JOURNAL

CONVERTING BETWEEN WRITE -

WHITE, WRITE - BLACK, AND U.S. C1.358/477 NEUTRAL BITMAPS
Reiner Eschbach

Proposed Classification

Int. C1. H04N 1/24

-ERODE/ DILATE DATA

1 I . 16 1

G ( K,O

h

I

OUTPUT I rlG'(K'e), .

QUANTIZE DEVICE

18 20 22

I

FIG. 1

XEROX DISCLOSURE JOURNAL - Vol. 17, No. 3 May/June 1992 181

[This page contains 1 picture or other non-text object]

Page 2 of 8

CONVERTING BETWEEN WRITE -WHITE, WRITE - BLACK, AND NEUTRAL BITMAPS(Cont'd)

FIG. 2

AylL

FIG. 3

182 XEROX DISCLOSURE JOURNAL - Vol. 17, No. 3 May/June 1992

[This page contains 1 picture or other non-text object]

Page 3 of 8

CONVERTING BETWEEN WRITE -WHITE, WRITE - BLACK, AND NEUTRAL BITMAPS(Cont'd)

FIG. 4

FIG. 5

XEROX DISCLOSURE JOURNAL - Vol. 17,wo. 3 May/June 1992 183

[This page contains 1 picture or other non-text object]

Page 4 of 8

CONVERTING BETWEEN WRITE -WHITE, WRITE - BLACK, AND NEUTRAL BITMAPS(Cont'd)

Two types of electrophotographic systems are well known, a first system, commonly referred to as a write-white or charged area development system, uses a laser to dissipate charge on the photoconductive surface in areas where development or printing is not desired. Thus, it might be said that white pixels are written to the photoconductive surface. In a second system, commonly referred to as a write-black or discharged area development system, the laser dissipates charge on the photoconductive surface in areas where development or printing is desired. Thus, it may be said that black pixels are written to the photoconductive surface. While each system is capable of producing a high quality reproduction. both have a distinct artifact occurring as a result of the imaging process. Write-white systems tend to shrink or erode black lines, while write-black systems tend to expand black lines. The change in line width can lead to the breaking of letters for small fonts in write-white printers, along with the overall appearance of the printed image appearing to be too light. For write-black printers, the result may be a closing of small letters, along with the overall appearance of a printed image appearing too dark.

Accordingly, the present invention provides a method of pre-compensating a bitmap of a binary image defined with pixels k X C at a first resolution, and a pixel depth of two levels, to account for erosion or dilation effects of an imaging process, where k represents the number of pixels in a scan line parallel to a fast scan direction, referred to as x-direction, and C represents a number of scan lines or rasters of pixels in a slow scan direction, referred to as y-direction. The method accounts for dilation or erosion by increments not equal to a pixel distance and includes the steps of: (1) increasing the number of pixels or resolution at which the bitmap is defined from k X C, to Kk X LC, where K and L are multipliers, thereby increasing the resolution of the bitmap by the same factors while keeping the area constant, i.e: input...