Browse Prior Art Database

PSEUDO ERROR DIFFUSION VIA HIGH FREQUENCY LINE SCREENING AND RANDOM NOISE

IP.com Disclosure Number: IPCOM000027728D
Original Publication Date: 1999-Feb-28
Included in the Prior Art Database: 2004-Apr-09
Document File: 2 page(s) / 107K

Publishing Venue

Xerox Disclosure Journal

Abstract

Disclosed is a change to an integrated circuit chip set photo-rendering algorithm from a dot screen to a high frequency line screen with random noise, thereby ensuring that the quality of reproduced text is less objectionable.

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XEROX DISCLOSURE JOURNAL

PSEUDO ERROR DIFFUSION VIA HIGH FREQUENCY LINE SCREENING AND RANDOM NOISE
Thomas A. Sanderson
Elizabeth A. Richenderfer

Proposed Classification
U. S. C1. 399/148 Int. C1. G03g 15/22

Disclosed is a change to an integrated circuit chip set photo-rendering algorithm from a dot screen to a high frequency line screen with random noise, thereby ensuring that the quality of reproduced text is less objectionable.

The application of a high frequency line screen with added random noise to pixels classified as continuous tone in an auto-segmented scanned image solves several problems. Under current segmentation methods implemented in electrophotographic printers, the lead edge of text characters is often misclassified as a continuous tone. In order to obtain optimal quality for text portions of an image, it is necessary to severely compromise the quality of photographic regions to mask these misclassifkations. If continuous tones are processed correctly and a halftone applied, objectionable jagged edges appear on the lead edge of text characters. These jagged edges are even more visible because of the periodic nature of the halftone dot. A solution to this problem is to create two separate modes of operation for the integrated circuit chip set, one which reproduces text well and photographs poorly, and one that reproduces photographs well and text poorly.

Currently, the text-biased mode of the chip set typically applies a threshold to photographs in order to obtain optimal text quality. In one application, the "Auto Mode" improves the quality of photographs rendered in the text biased mode somewhat over the "Text and Halftones Mode" by applying random noise to threshold photographs. This still, however, produces image quality far below desired levels.

The disclosed process solves this problem in the following manner. By rendering regions classified as photographs with a...