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Gray Scale Image Compression Algorithm

IP.com Disclosure Number: IPCOM000047226D
Original Publication Date: 1983-Oct-01
Included in the Prior Art Database: 2005-Feb-07

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Greenhalgh, RC [+details]


This article describes a run-length encoding algorithm including vertical reference coding. Unique code patterns are transmitted where a current string of black or white pel values correlate with a string in the preceding or history line. Correlation is defined as a condition where successive lines have strings of the same value (black or white) which begin at the same pel and end within one pel of each other. Table 1 below defines eight (type A - type H) signal types. A type A signal specifies a gray scale value for a single pel. Signal types B, C, and D are used where a correlation is found between the current line and the history line. Signal types E, F, G and H define both short and long runs of white and black pels in those instances where no correlation exists.