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Pseudo Halftone for Representing Continuous Tone Images in Black White Facsimile Systems

IP.com Disclosure Number: IPCOM000092452D
Original Publication Date: 1966-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Machol, GK: AUTHOR

Abstract

This facsimile technique divides up an image area into small arrays of sample points and codes each sample point successively either black or white independently of past sample points. The resulting representation is similar to a halftone image in which the image area is divided up into small identical squares. The average blackness of the original image in each square is represented by a single dot having the appropriate area. Thus, if each array comprises a 2 x 2 matrix of sample points, the degree of blackness of the image in each region is represented by making the values 0, 1, 2, 3, or 4 within the array black.

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Pseudo Halftone for Representing Continuous Tone Images in Black White Facsimile Systems

This facsimile technique divides up an image area into small arrays of sample points and codes each sample point successively either black or white independently of past sample points. The resulting representation is similar to a halftone image in which the image area is divided up into small identical squares. The average blackness of the original image in each square is represented by a single dot having the appropriate area. Thus, if each array comprises a 2 x 2 matrix of sample points, the degree of blackness of the image in each region is represented by making the values 0, 1, 2, 3, or 4 within the array black.

Drawing 1 shows a portion of an image separated by dashed lines into the small arrays, the sample points being labeled a, b, c, or d. Assuming 8-level quantization, each sample value is transformed into white 0 or black 1. This is done using the table of drawing 2. In this table, for example, if the sample value is 011, the transformed value is 1 if the sample point corresponds to a or b in drawing 1 and is 0 otherwise. The entries p mean that the transformed value can either be 1 or 0 as determined by some pseudorandom device in which the probability of generating a 1 is p. Examples of applying the transformation represented by drawing 2 are shown in drawing 3 in which black dots are used to represent 1's.

Other tables, similar to the one given, and division into...