Two-dimensional method and system for compressing bi-level image

Details Two-dimensional method and system for compressing bi-level image Two-dimensional method and system for compressing bi-level image

1994-09-20

1997-04-01

Coles, Sr., Edward L.

395115, 395112, G06K 1500

Patent

active

056175175

ABSTRACT:
A two-dimensional compression method and system for compressing a bi-level bit-mapped image. The compression system reads a current row of data from the bit-mapped image and compares the current row with the row immediately preceding the current row, called the reference row. If a byte in the current row is equal to a corresponding byte in the reference row, then the byte is represented by a COPY mode and the byte is copied from the reference row to a compressed row. If the byte is not equal to the byte in the reference row, then the next byte in the current row is read and compared with the preceding byte. If the current byte equals the preceding byte, then the byte is represented by a REPEAT mode and copied to the compressed row along with a count of how many times to repeat the byte. If the current byte is not equal the preceding byte, then the byte is represented by a LITERAL mode and the byte is copied directly to the compressed row along with a count of how many bytes are to be copied. Each transition from one mode to another in the compressed row is assigned a variable-length mode code, and each count in the compressed row is assigned a variable-length count code. The current row, once compressed contains a sequences of triplets comprising a mode code followed by a length code, and optionally followed by one or more data bytes.

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