Method and apparatus for processing picture element (pel) signals of an image.

摘要

An original image of a text document is scanned by an image scanner of a resolution of 240 pel/inch in a terminal device. The image scanner generates binary data for each pel of the image sampled at the 240 pel resolution which are stored in a input image buffer. The pel signals are selectively fetched to generate a first compressed data stream 120 pel resolution and a second compressed data stream of the remaining pels. To selectively fetch the pel signals four sampling windows are prepared. The first window fetches one pel signal, as a current pel signal being processed, stored at one of every other pel position and a plurality of neighbouring pel signals stored at the every other pel positions. The sampling points of the first window are arranged at 120 pel resolution. Second, third and fourth sampling windows are used to fetch or sample both pel signals at 120 resolution and the remaining pel signals in various combinations. Patterns of the second, third and fourth windows differ from each other and are arranged at 240 pel resolution.