EP0454274A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Method for controlling halftone dot shape during dot growth

Assignee: Bayer Corp

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Filing: 1991-04-24

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Granted: —

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Expires: 2011-04-24

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Abstract

Abstract A method for controlling half-tone dot shape during dot growth is disclosed. The x and y coordinate values for a screen cell are determined. The shape of the 50% anamorphically or symmetrically square dot is rotated into alignment with the x and y vectors of the screen cell. The Cartesian x and y coordinate values are converted into a non-linear polar coordinate system to vary dot shape as the dot grows from 0% to 100%. The dot shape is approximately circular close to the origin and gradually becomes squares at 50% and then gradually returns to circular at 100%. Further, processing using reverse rotation and conversion back to the Cartesian coordinate system can be utilized to obtain elliptically shaped dots.

Inventors

👤 Paul A. Delabastita

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-11-01 13:29

CPC Classifications

H; H04; H04N; H04N1/00; H04N1/40; H04N1/405; H04N1/4055

Claims Analysis

Total Claims: 3

Claim 1

Independent Claim 119 words

A method for controlling half-tone dot shape during dot growth in an electronic half-tone screening process, said method comprising the steps of: A. determining the X and Y coordinate values for a screen cell; B. rotating a 50% anamorphically or symmetrically square dot shape in the screen cell into alignment with the X and Y vectors of the screen cells; C. converting the X and Y coordinate values into a non-linear polar coordinate system where: radius = (1.0 - cos(pi * x) * cos(pi * y))/2.0 if (x > 0.0)angle = artan(y/x) if (x < 0.0)angle = artan(y/x) + pi; and, D. utilizing as screen function, the value "s" where s = sqrt(x * x + y * y).

Claim 2

Independent Claim 150 words

A method for controlling half-tone dot shape during dot growth in an electronic half-tone screening process, said method comprising the steps of: A. determining the X and Y coordinate values for a screen cell; B. rotating a 50% anamorphically or symmetrically square dot shape in the screen cell into alignment with the X and Y vectors of the screen cells; C. converting the X and Y coordinate values into a non-linear polar coordinate system where: radius = (1.0 - cos(pi * x) * cos(pi * y))/2.0 if (x > 0.0)angle = artan(y/x) if (x < 0.0)angle = artan(y/x) + pi; D. converting the non-linear polar coordinates back to Cartesian system coordinates; E. rotating in a reverse direction and by the same angular amount as Step B the resulting dot shape; and, F. utilizing as a screen function, the value "s" where s = sqrt(x * x + y * y).

Claim 3

Independent Claim 148 words

A method for controlling half-tone dot shape during dot growth in an electronic half-tone screening process, said method comprising the steps of: A. determining the X and Y coordinate values for a screen cell; B. rotating a 50% anamorphically or symmetrically square dot shape in the screen cell into alignment with the X and Y vectors of the screen cells; C. converting the X and Y coordinate values into a non-linear polar coordinate system where: radius = (1.0 - cos(pi * x) * cos(pi * y))/2.0 if (x > 0.0)angle = artan(y/x) if (x < 0.0)angle = artan(y/x) + pi; D. rotating in a reverse direction and by the same angular amount as Step B the resulting dot shape; E. converting the non-linear polar coordinates back to Cartesian system coordinates; and, F. utilizing as a screen function, the value "s" where s = sqrt(x * x + y*y).

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