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Method and apparatus for delta row decompression
| Details |
Inventors: Vondran, Jr., Gary L.;
Assignee: Hewlett-Packard Company (Palo Alto, CA)
Primary Examiner: Powell; Mark R.
Assistant Examiner: Garcia; Gabriel I.
Attorney, Agent or Firm:
A hardware implementation of a method of decompressing delta row compressed data to uncompressed data having line buffer memory 70 with incrementally advanceable current address 72. Offset counter 78 is used to determine the number of repeating bytes of data stored in line buffer memory 70 for a first row are to be reused in a second row, and replacement counter 76 is used to store the number of sequential replacement data bytes. A RAM controller state machine 84 reads data bytes from line buffer memory 70 to a laser printer engine, and after reading, checks through decompression state machine 82 to determine if a replacement data byte is called for at the current address in the next row of data, writing it in if called for, otherwise, merely incrementally advancing to the next current address in the line buffer memory. |
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DETAILED DESCRIPTION I claim: 1.
A circuit for decompressing delta row compressed data, having command data bytes containing information as to the location and number of replacement data bytes, and replacement data bytes, which in combination with a first row of uncompressed data bytes, together reflect the changes from said first row of uncompressed data bytes directly usable by a laser printer engine in a laser page printer, to render a second row of uncompressed data bytes directly usable in a laser printer engine, which comprises: a line buffer memory for storing said first row of uncompressed data bytes; means for identifying, from information contained in the command data byte, the location and number of data bytes within the first row of data bytes to be replaced with replacement data bytes to form a second row of uncompressed data bytes; means for sending, seriatim, the data bytes of the first row to said laser printer engine; means for deriving said second row by each identified data byte of the first row with a replacement data byte as each identified data byte of the first row is sent to said laser print engine.
2.
The circuit of claim 1 wherein the means for sending and the means for replacing further comprise: a memory controller state machine for, upon receiving an engine data request from a laser printer engine, Reading data from a current address in said line buffer memory, determining whether said current address is to be the location of a replacement data byte in a second row of uncompressed data bytes, and if it is to be the location of a replacement data byte in said second row of uncompressed data bytes, then Writing said replacement data into said current address within said line buffer memory and then incrementing the current address to the next address within said line buffer memory, or if the current address is not to be the location of a replacement data byte in said second row of uncompressed data bytes, then incrementing the current address to the next address within said line buffer memory
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Image Analysis 
