Bitstream Inc.

Philip G Apley

John S Collins

David A Berlow

Michael Yudis

An outline representation of a character or symbol is treated as being composed of a set of zones formed in both the horizontal and vertical directions. The zones are completely character-specific. Each zone defines the extent of some feature of the character. The boundaries of the zones are mapped to specific pixel locations in a bitmap em-square of selected resolution and size. Additional interpolation zones are defined which are used to map all the points on the outline representation of the character that are contained within the interpolation zone, but do not coincide with a control edge, from the positions in the high-resolution em-square to a corresponding position in the low-resolution em-square. To maintain relationships between features, constraint functions may be defined which regulate the size of the control zones for a character at predetermined sizes. Control zones and interpolation zones are all derivatively linked to a basic set of horizontal and vertical control edges at the outline description level. Consequently, the number of computations needed is reduced and the speed with which a bitmap can be generated from the outline representation is increased.

Method and apparatus for conversion of outline characters to bitmap

A system and data structure for generating bitmap representations of characters and symbols from their outline representations. The outline representation is treated as being composed of a hierarchy of zones formed in both the horizontal and vertical directions. The zones are completely character-specific. Each zone defines the extent of some feature of the character. The zonal definition of the character comprises part of the information in the data structure. In generating the bitmap, the boundaries of the zones are mapped to specific pixel locations in a bitmap em-square of selected resolution and size. The available pixels are then allocated to the zones. After each level of zone has received its pixel allocation, the pixels assigned thereto are then distributed among the next lower level of zones and the process is repeated iteratively until all zones have received their pixel allocations or it is no longer possible to make allocations. To maintain relationships between features, features of characters (both within individual characters and between different characters) may be linked in the data structure so as to be defined in terms of the features of the same or other characters. The features are linked at the outline description level, so that the linking need be specified only once and will thereafter be useful any time a bitmap is to be generated from the outline.

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Allston, MA, United States of America

Philip G Apley