Adobe, Inc.

John P Felleman

Richard A Dermer

Mark C Hamburg

Thomas F Knoll

James J Estrada

Richard G Rocheleau

Methods and apparatus, including computer program apparatus, implementing techniques for preparing a region of an electronic document for printing on a printing device having asymmetric misregistration behavior. The techniques include trapping the region asymmetrically to compensate for asymmetric misregistration behavior of a printing device. The region can be an entire page or a portion of a page represented in a page description language or a raster representation. The techniques can include defining an asymmetric transformation; applying the asymmetric transformation to the region to generate a transformed region; processing the transformed region to generate transformed traps; and applying an inverse transformation to the transformed traps to generate traps for the region, the inverse transformation being an inverse of the asymmetric transformation. Defining the asymmetric transformation can be done by obtaining a first trap width magnitude and direction, the first trap width being a minimum trap width for the device; obtaining a second trap width magnitude and direction, the second trap width being a maximum trap width for the device; defining a rotational component of the asymmetric transformation by determining an angle by which a first axis of a device space has to be rotated to be aligned with the first trap width direction; and defining a scaling component of the asymmetric transformation according to a ratio of the first trap width magnitude and the second trap width magnitude.

Creating traps with asymmetric widths

The invention provides a method and computer program of instructions for specifying a device independent trap color in a color space for a color boundary. The method includes obtaining a first color value (C), representing a first color in a color space associated with the color boundary, having a first darkness and first chromaticity and obtaining a second color value (C), representing a second color in the color space associated with the color boundary, having a second darkness and second chromaticity. The method includes generating a trap color value, representing a color in the color space, having substantially a same darkness as a lighter of the first and second color value, and a chromaticity that is a function of the first and second chromaticities of the first and second color values.

Device independent trap color specification

A computer-implemented method traps an edge in a color page described by page data, independently of the output device. The method comprises identifying, based on page data for a color page, an edge and first and second adjacent regions having the edge as a common boundary. defining a clip region, including the edge and at least part of one of the first and the second regions, and generating and storing device-independent trap data representing the clip region for use by an unspecified output device for trapping the edge. A page trapped by the method for output on an unspecified output device includes trap data for at least one edge represented in the page, the trap data for each edge comprising edge data, defining the edge, adjacent region data, describing a first and a second adjacent region sharing the edge as a common boundary, and clip region data, defining a clip region including the edge and at least part of the first or the second adjacent regions.

Device-independent trapping

A look-up table of ink density values corresponding to a predetermined number of printed bit patterns is used to convert a high resolution bi-level data file into a lower resolution contone data file. A method to convert bi-level data to contone data includes reading a specified number of words from the bi-level data and retrieving, for each word, an ink density value from the look-up table using the word as an index into the table.

Bi-level to contone data conversion

Methods and apparatus for determining the allocation of a trap width to the spread of a pair of inks in printing. Allocation of the spread is based on both a solidity value that may be between zero and one and a lightness value. The technique may be applied to an arbitrary number of inks by considering each pair of inks separately.

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Palo Alto, CA, United States of America

John P Felleman