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Abstract

A method and apparatus for storing compressed bit map images in a laser printer. Bit map images representing a page of data are divided into bands and compressed into the printer memory. Then, when needed by the interpreter/rasterizer, they are decompressed into another portion of that memory, or when desired to print those bands they are directly transmitted to a decompression engine. The bands of bit map image are compressed using a Lempel-Ziv algorithm that contains improvements allowing compression towards the end of the band and improves the compression speed at the beginning of the band by initializing a hash table. Further, the interpreter/rasterizer switches between compression routines depending on the available memory and the desired speed of compression. The compression routine requests supplemental destination buffers when it needs additional memory in which to compress data. Finally, the compression continues to add margin white space during the compression of the uncompressed bit images so that margin what space need not be stored in the uncompressed bit image.

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First Claim