Graphic Edge, Inc.

Adobe, Inc.

Aldus Corporation

Alan Blannin

Keith R Deutsch

Per H Bjorge

Timothy H Roth

Eric J Bean

Douglas L Peltonen

A trapping technique that accepts a Postscript or other page description language (PDL) file and outputs a file in PDL format having the correct traps. The input page is first divided into subportions, or tiles, and the tiles are individually processed by evaluating the input file in a corresponding dipping window. Each tile is then analyzed to determine the presence of boundaries or intersections between page objects or color regions. A trapping analyzer generates trap vectors in accordance with a set of desired trapping rules which take into account existing traps and the proximity of other page objects. In a preferred embodiment, the trap vectors are then convened to PDL form.

Applying traps to a printed page specified in a page description

A trapping technique which accepts a Postscript or other page description language (PDL) file and outputs a file in PDL format having the correct traps. The input page is first divided into sub-portions, or tiles, and the tiles are individually processed by evaluating the input file in a corresponding clipping window. Each tile is then analyzed to determine where edges exist. The edge data is fed to an edge converter which produces a list of color transitions consisting of the analytic description of each edge and the color information along the sides of the edge. The color transition information is fed to a trapping analyzer which generates trap vectors in accordance with a set of desired trapping rules. The trap vectors are then converted to PDL form. As a final step, the trap vectors are added to the original PDL file. The final trapped page may be printed on standard typesetters without the need for special trap generator hardware.

A technique for developing an analytic model of an image by operating directly upon the pixel map representation output by an optical sampling device, such as a scanner. The resulting analytic representation is hierarchical, below a certain level, with each element an analytic expression representing a portion of the image. Above a certain level, the model is a simple array, to facilitate certain types of graphical manipulations. The model is developed by arranging pixel values into a number of groups called tiles. A number of operations are then performed on each tile, to determine how it can best be represented as an analytic expression. For example, if all pixel values in a tile are approximately continuously varying, they be represented as a three-dimensional linearly sloped surface. However, if one or more intensity boundaries run through the tile, analytic expressions, such as a straight line or a parabolic line segment, are derived from the tile's pixel values to describe the edges.

Technique for representing sampled images

A technique for creating and applying half tone screen patterns by computer, consisting of a screen generator and a screen applicator. The screen generator accepts a set of parameters specifying the angle and frequency of the desired screen, the output printing device resolution, and parameter tolerances. It then produces a half tone screen pattern file according to the specified parameters, as a set of repeat arrays for each desired gray level. The screen applicator accepts an input contone image representation such as is produced by a scanner or other device, and the half tone screen pattern file produced by the screen generator. It then interpolates between the pixel values, at the output device resolution, by examining the repeat arrays for each device cell. In this way, a representation of a half tone screening of the input contone image results where the output device resolution is fully exploited.

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Amherst, NH, United States of America

Alan Blannin