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Intelligent Threshold and Two Dimensional Interpolation of Staggered Array Sample Data

IP.com Disclosure Number: IPCOM000089374D
Original Publication Date: 1977-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Stucki, P: AUTHOR

Abstract

At scanning resolutions < 96 L/inch, the digital representation of typewritten alphanumeric symbols becomes badly misshapen. To improve the reproduction quality of such low-resolution scan data, interpolation techniques in combination with higher resolution printing can be used.

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Intelligent Threshold and Two Dimensional Interpolation of Staggered Array Sample Data

At scanning resolutions < 96 L/inch, the digital representation of typewritten alphanumeric symbols becomes badly misshapen. To improve the reproduction quality of such low-resolution scan data, interpolation techniques in combination with higher resolution printing can be used.

A new approach is to delay the sampling instants T(s) along even lines by Tau = T(s)/2 as compared to those along odd lines. The staggered sampling patterns obtained lend themselves well for local pre-processing to improve quality when needed.

Thresholding for bilevel quantization is made in an intelligent manner by digitizing the scanned data f(x,y) into Qmax amplitude quantization levels, taking a binary decision f`(x,y) and memorizing a positive or negative error or difference value Delta f(x,y) to update three neighbor elements f(x + 1,y), f(x,y + 1), f(x - 1,y + 1) with a correction value.

If Qmax/2 < f(x,y) </= Qmax, then f`(x,y) = `1' (black), Delta f(x,y) = f(x,y) - Qmax.

If 0 < f(x,y) </= Qmax/2, then f`(x,y) = `0' (white), Delta f(x,y) = f(x,y). f(x + 1,y) ---> f(x + 1,y) + k(1) Delta f(x,y) f(x,y + 1) ---> f(x,y + 1) + k(2) Delta f(x,y) f(x - 1,y + 1) ---> f(x - 1,y + 1) + k(3) Delta f(x,y) where k(1), k(2) and k(3) are experimentally determined directional weighting factors (Fig. 1).

Intelligent thresholding in a staggered sampling environment provides a low- resolution, bilevel representati...