Abstract: A system for clearing a buffer for holding bitmap data output by a decomposer or interpreter in a digital printing apparatus exploits a decompressor chip. Instead of having the processor directly write blank data into the buffer to clear the buffer, a "buffer clear" software utility sends compressed blank image data to the decompressor chip, which in turn decompresses the blank image and writes the decompressed blank image to the necessary location in the buffer.

Abstract: In a real-time printing system, in which large blocks of digital data corresponding to page images must be located in a memory via a translation table and accessed from the memory within a very narrow time frame, the memory-management internal program of an operating system is overridden by external instructions which lock the translation table in memory.

Abstract: A high-volume digital print service has a plurality of independent and simultaneously-operable decomposers which each output decomposed image data to a common buffer. The decomposed data can be compressed for relatively long-term retention in the buffer, by means of a compression element. All of the decomposers and the compression element are operated by a central CPU facility. A control system, sensitive to the amount of data in the buffer at a given time, apportions CPU cycles among the decomposers and compression element for optimization of the entire print service. The control system can also command printing hardware to skip pitches on an imaging surface therein, in order to reduce demand for decomposed data.

Abstract: A digital printing system includes a plurality of decomposers which operate simultaneously and independently. Each decomposer outputs page images of decomposed data at essentially random times. The page images from the decomposers are retained in a buffer until requested by a marker which controls the printer hardware. A buffer manager records where in the buffer each page image is stored, and a stream handle is assigned to every set of page images intended to form a multi-page document. When the marker requests a particular set of page images for printing, the marker invokes a stream handle. The buffer manager, receiving the stream handle, retrieves the necessary page images from recorded locations in the buffer.

Abstract: A digital printing apparatus accepts image data in the form of PDL files, and also instructions, external to each PDL file, about shifting images formed at the PDL file to precise positions on a print sheet. The PDL file is interpreted to yield a raw bitmap, and then compressed according to a compression algorithm. The external shift instructions are then included in the compressed data as blank-line instructions which add a number of blank lines equal to a number of scan lines the image is desired to be shifted. The shifting is useful for accommodating bindings in the finished printed documents.

Abstract: In a high-speed digital printing apparatus having duplex capability, second-side images must be rotated. In order to quickly rotate the second-side images, the image data for the images are read out from memory in a reverse order of addresses, with each address corresponding to one byte. As each byte is transferred to an imager, a relationship of sets of bits, each set of bits corresponding to one pixel, are altered within each byte.