Patent
1997-03-11
1999-07-27
Boudreau, Leo H.
395115, G06K 1500
Patent
active
059304669
ABSTRACT:
An improved printing system is provided that compresses bitmap print data by determining, per each vertical slice of a horizontal swath of the printed page, which one of two different data compression techniques to more efficiently compresses each individual slice, then temporarily stores this compressed data in a memory circuit until needed by the printhead for actual printing of the final output in the form of print media. When using slices containing seven (7) different words per slice, the present invention utilizes a single "control bit" of a "control word" to represent each of the data words of the slice. Depending upon which type of compression technique is used, the control bit for each data word will be set to either Logic 1 or Logic 0, depending upon the value of the data word as compared to a pre-determined data word value that is chosen by the system, and which may be used in both types of data compression techniques. After each slice has been analyzed by both types of data compression techniques, certain of the data words in the slice can be temporarily discarded, leaving behind less than seven (7) data words to represent that slice as compressed data. This compressed data for each individual slice will be matched up with a "control word" that is made up of the individual control bits described above, thereby creating a relatively small data set that can be stored in memory in a space that would be less than the amount of memory required to store the uncompressed slices for the same print data. Later, these (compressed) data sets (one per individual slice) can be decompressed according to the proper decompression technique, and the full print data is then restored just before printing by the printhead. As part of the control word, a "mode bit" can be set to either binary value of Logic 1 or Logic 0, thereby indicating which of the two data compression techniques was initially used for that slice. The two data compression techniques used are called a "USE-X MODE" and a "REPEAT MODE."
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Aust Ronald K
Boudreau Leo H.
Gribbell Frederick H.
Lexmark International Inc
Mehta Bhavesh
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