David R Clemens, Age 784318 Sandhurst Way, Rocklin, CA 95677

5305395, Apr 19, 1994

Jun 8, 1990

7/535438

James V. Mahoney - Sunnyvale CA
David T. Clemens - Somerville MA

Xerox Corporation - Stamford CT

G06K 900

382 27

Near neighbor data is produced hierarchically for each pixel of an image. Each pixel's near neighbor data indicates the presence of an approximate near neighbor pixel in each of four quadrants with respect to the pixel, and can also indicate distance and orientation to the near neighbor pixel. The near neighbor data can be produced by parallel processing units, with each processing unit producing, for a respective pixel, a near neighbor data item at every level of the hierarchy. Each near neighbor data item can indicate the presence of an approximate near neighbor in a respective region of the image. A near neighbor data item for a higher level region can be produced by selecting between near neighbor pixels indicated by near neighbor data items for subregions at the next lower level, by choosing the near neighbor pixel that is nearer. The quadrants can be asymmetric so that each pixel is not included in any of its four quadrants and so that the quadrants do not overlap. To provide accurate near neighbor data for a black pixel, the near neighbor data can be shifted to the black pixel from the adjacent pixels, each at the origin of one of its quadrants.