Hewlett-packard Development Company, L.P.

Hewlett-packard Company

Richard H Benear

Randall Don Briggs

Jeffrey L Trask

Brian E Hoffmann

Scott C Clouthier

James R Nottingham

Gregory Alton Vaughn

James A Kazakoff

Clayton E Chadez

David S Pitou

Rulon Gregory Esplin

Jeffery M Roberts

Rulon G Esplin

Gregory S Saathoff

Compression apparatus is described that operates to select an optimum compression procedure to apply to received image data. The compression apparatus can be employed in a page printer having a print engine that must be provided with video data at a constant rate in order to avoid a print underrun. The page printer operates to receive print data and to convert the received print data into rasterized page strips. Some or all of these rasteized page strips can then be compressed by the compression apparatus for later conversion to video data. The compression apparatus operates to compress each received rasterized page strip by selecting a compression procedure that results in a compressed strip that will provide optimum print quality while not causing a print underrun and that is below a threshold data size.

Method and apparatus for data compression

An alignment apparatus for use in an electrophotographic imaging device includes a first counter to count a first value of changes of a first signal, with the first value related to a first location of a photoconductor in a first direction. In addition, the alignment apparatus includes a second counter to count a second value of changes of a second signal, with the second value related to a second location of the photoconductor in a second direction substantially perpendicular to the first direction. Additionally, the alignment apparatus includes a circuit coupled to the first and the second counter to generate a change in a third signal after the first and the second counter count to, respectively, the first value and the second value.

Method and apparatus for alignment of image planes

A method and apparatus enhance a color or grayscale raster image in a printer by identifying a working pixel in the raster image for anti-aliasing, and then modifying luminance data of the working pixel in a luminance chrominance color space such that an anti-aliasing effect is achieved relative to the raster image. The luminance component of the raster image data is converted to a binary format to identify the working pixel using RET template matching. The luminance data of the working pixel is modified by utilizing luminance data of adjacent pixels to produce a new luminance value which is then assigned to the working pixel. One of the adjacent pixels defines an edge of the object being anti-aliased in the raster image, and the other of the adjacent pixels defines an edge of a region in the raster image that is adjacent the object. In the event chroma data is associated with the object, the chroma data is combined with the modified luminance data and also assigned to the working pixel for accurate imaging thereof.

Luminance-based color resolution enhancement

A printer performs both the processing and printing tasks efficiently using controller firmware with a single data path (i.e., one ASIC). The printer has a periodic print cycle in which data for one page or plane (if multi-colored) is printed during each cycle. The print cycle is typically longer than the time needed to print one page or plane. Thus, the print cycle can be segmented into a &ldquo;printing phase&rdquo; in which the printing mechanism prints data, and a &ldquo;non-printing&rdquo; phase in which the printing mechanism does not print data. The controller firmware interleaves printing operations with non-printing operations during the printing and non-printing phases of the print cycle, respectively. During the printing phase, the controller is dedicated to printing a page or plane. During the non-printing phase, the controller is free to perform other tasks, such as compressing raster data for subsequent printing. The printer is configured with a set of operating parameters that enable the controller firmware to alternate between printing and non-printing tasks (e.g., data compression). Once released from manufacturing, the printer may, in practice, not perform optimally to the specifications. Thus, another aspect of this invention is to tune the operating parameters to achieve optimal performance for a specific printer. This tuning is a self-tuning technique that is performed in post-manufacture real-time, while the printer is in operation.

Printer and method for alternately printing and compressing data using same processing unit

Apparatus for writing compressed data to a storage device having multiple storage areas. The apparatus identifies one or more storage areas to receive the compressed data based upon the compression ratio of the compressed data and the characteristic transfer rates of the storage areas. The apparatus then writes the compressed data to the Identified storage areas. This is accomplished so that when the compressed data is later read, the storage device has at least a minimum output rate. The storage device may, for example, be a disk storage unit for a laser printer. The compressed data may be compressed video data describing a document to be printed.

Apparatus and method for storing compressed data to a storage device

Fine pulse width modulation (PWM) adjustments in the output of a laser printer are accomplished by receiving values from a bit map and modifying the values in accordance with values in a lookup table (LUT). The lookup table is subdivided into a plurality of blocks, and a selection of the blocks is made in accordance with external values. This allows the output of a pulse width modulation circuit to be adjusted to a precision that is greater than that afforded by the bit size of the values from the bit map. The use of plural blocks in the lookup table permits adjustments in the output of the pulse width modulation circuit in accordance with external factors such as relative humidity, sensitivity of an optical photoreceptor, and developer life.

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Boise, ID, United States of America

Richard H Benear