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A TECHNIQUE TO GUARANTEE 2:l COMPRESSION AND ENHANCEMENT OF HALFTONE PICTURES

IP.com Disclosure Number: IPCOM000024332D
Original Publication Date: 1980-Apr-30
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 109K

Publishing Venue

Xerox Disclosure Journal

Abstract

In a general image transmission system using data compression, an image input terminal scans the image, quantizes the data and compresses it prior to transmission or storage. The transmission or storage bandwidth is typically less than that of the input terminal so that a guaranteed real time minimum compression ratio, n, is required.

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~EROX DISCLOSURE JOURNAL

A TECHNIQUE TO GUARANTEE 2:l COMPRESSION AND ENHANCEMENT OF HALFTONE PICTURES
Henry H. Liao

Proposed Classification
U.S. C1. 358/283
Int. C1. H04n 1/40

In a general image transmission system using data compression, an image input terminal scans the image, quantizes the data and compresses it prior to transmission or storage. The transmission or storage bandwidth is typically less than that of the input terminal so that a guaranteed real time minimum compression ratio, n, is required.

The proposed system is based on a two dimensional n x n matrix where each cell represents a binary pixel as shown in Figure 1.

n

n

Figure 1

For simplicity of description, let n = 4. A halftone picture can be segmented into a number of 4 x 4 boxes. All boxes are connected side by side. Statistically, the halftone dot can be classified into regular and irregular dots represented by the examples of Figure 2.

Figure 2

Regular Halftone Dot Irregular Halftone Dot

An irregular dot is not an impossible dot. It is not a partial dot either. It is caused by unusually high, irregular frequencies in the continuous tone original, which cannot be represented by regular halftone dot frequencies and which should have been filtered out in the beginning. In other words, these irregular dots are meaningless to the original intent of halftone rendition and may be substituted without the observer's notice. In some cases, the substitution may even enhance the halftone picture.

Volume 5 Number 2 March/April 1980 205

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A TECHNIQUE TO GUARANTEE 2:l COMPRESSION AND ENHANCEMENT OF HALFTONE PICTURES (Cont'd)

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In general, there are 64k binary patterns in a 4 x 4 matrix. However, it isunlikely that all possible patterns will exist and most of the low-frequency patterns should be classified as irregular patt...