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Optimal Digital Halftone Pattern Generation Method

IP.com Disclosure Number: IPCOM000082894D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Stucki, P: AUTHOR

Abstract

Known methods or producing halftone representations of continuous-tone pictures by digital techniques include concentric dot-pattern modulation, dot-pattern size modulation and random dot-pattern modulation.

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Optimal Digital Halftone Pattern Generation Method

Known methods or producing halftone representations of continuous-tone pictures by digital techniques include concentric dot-pattern modulation, dot- pattern size modulation and random dot-pattern modulation.

The improvement on these known methods involves uniformly dispersed dot- pattern modulation consisting of a uniformly distributed assignment of black dots to the individual cells of a halftone picture element, as a function of the grey tone to be reproduced.

A unique set of Q fixed threshold patterns consisting of A/2/ integer random numbers between 1 and Q is produced. If the integer random number at a given cell of a halftone picture element is higher than or equal to the continuous-tone value at that cell, a black dot is written there.

For halftone picture elements containing A/2/ cells, where A = 2/i/ and i = 1,2,3..., a fixed threshold matrix is built up in accordance with this process: The A/2/ cells are first divided into 2/2/ equal-sized arrays each comprising M(1) = A/2//2/2/ cells. If M(1) >1, the arrays are each further divided into 2/2/ subarrays of equal size, each comprising M(2) = A/2//2/4/ cells. The division is continued until A/2//2/2/ = 1.

Regular dot-pattern arrays representing a scale of halftones are then obtained by subtracting from a completely "black" halftone picture element, pairs of black dots in accordance with the following scheme: i = 1 A/2/ = 4 S(1)S(3), S(2)S(4), i = 2 A/2/ =...