Abstract: A run length codeword system which has a set of codewords, each codeword being one byte. The first codeword of a run is divided into a 4-bit code part and 4 bits of printing hints. The code part specifies the source of the data, and the format of the remaining bytes in the run. The remaining one or two codewords specify the number of remaining data bytes in the run, or color values.

Abstract: A digital color printing method and system is described which automatically detects when a neutral grey object is commanded to be printed, and changes the composition of the neutral color depending on the previous value of the neutral grey object and on the presence or absence of non-black colorants in the background color at the position on the page at which the neutral object is commanded to be printed. A single-color neutral object which is commanded to be printed at a position in which there is a previously rendered color background which contains non-black colorants may automatically have its neutral color changed from a single-color neutral to a process neutral containing at least one non-black colorant such as cyan, magenta, or yellow, said process neutral chosen to have equivalent visual density and neutrality as the previous single-color neutral value.

Abstract: A technique for producing high quality output on a mixed-resolution color printing device. Unlike current techniques that impose global ink-limit and dot scheduling constraints, the new method can improve the quality of text and line-art features by rendering the outline at the highest resolution yet maintaining an overall ink-limit by compensating the inside density. The new method uses a programmable unsharp mask filter to detect and outline these edges. The system uses bigger black drops than for the three colors, so the big drops have to be treated differently for avoid saturating the paper. The method allows a little saturation, selectively as necessary, and controls the drop spacing and color correction to minimize the problem for nearby pixels. The result is that the quality of rendering is superior to that of the current rendering methods, especially for text and fine line-art graphics. The technique also limits head heating.

Abstract: A circuit which uses less memory to store halftone arrays in a high addressability printer by storing regular halftone arrays as low addressability arrays and by outputting each pixel a number of times, the number being the ratio of high to low addressability. For example, if a high addressability system uses 4 sub pixels for each pixel, then one value of each low addressability array is stored in one location and the halftone circuit is controlled to output that value 4 times, once for each sub pixel thus saving memory by a factor of 4.

Abstract: A compression process of dividing each word to be compressed into least and most significant bits, and applying a different compression ratio to each. If the compression processes are lossy, both parts of the output can also be losslessly compressed before being output. Hierarchical vector quantization can be issued for either lossy compressor.

Abstract: Color printing systems frequently use multiresolution analysis, which creates intermediate lower resolution images, in applications such as descreening and filtering. The typical steps are to decompose the original image into sub bands, apply the application to one or more sub bands and then recompose the image, prior to color correction and color space transformation. This disclosure describes applying the color correction to one of the lower resolution sub bands and a simpler color space transformation to the final image as a way to reduce the amount of computation. The described multiresolution analysis is a wavelet transform.

Abstract: An impedance transport circuit, which is capable of transporting both AC and DC impedance, utilizes two PMOS transistors and two n-channel transistors with two operational amplifiers. The two operational amplifies cause the drain voltages of all transistors to be equal and therefore transport both the AC and DC input impedance to the output impedance.

Abstract: In a system having a PCI bus, an additional memory attached to the bus to allow a higher speed of data transfer for a number of copies from the computer to a number of devices. The additional memory has a number of DMA channels, each associated with an I/O device. One copy of the data required by an I/O device is transferred to the memory at normal computer FIFO speed. Thereafter, multiple copies of that data can be transferred to the I/O device from the memory at the higher data bus speed.

Abstract: An improved electric paper which allows it to form an image from a light image rather than from an applied electric field. The prior art embodiment had a number of rotatable balls imbedded in a plastic substrate. Each ball had hemispheres that had different electrical characteristics, and were colored differently. Under the influence of an image in the form of an electrical field, the balls would selectively rotate to form a permanent visible image, whereupon the field could be removed. This invention has two conductive surfaces to provide a uniform electric field across the substrate, and then exposes the substrate to light which selectively changes the electrical characteristics of one of the two hemispheres, resulting in the rotation of the selected balls to form the image.

Abstract: A system for producing non-copyable prints. In a xerographic printer, text is printed using clear toner. Thus, the only optical difference between toner and non-toner portions of the page is in the reflectivity. The plastic toner will reflect more light than the paper. A human reader can now read the image by holding the page at such an angle that the eye will intercept the reflected light from the toner, producing a contrast between the lighter appearing toner and the darker appearing paper. However, a copier scanner is always set up to avoid reflected light, by supplying light at an oblique angle and reading at a right angle. In this case the diffused light is approximately equal for both toned and untoned surfaces, the scanner will detect no difference and the copier will not be able to copy the original.

Abstract: A system for guaranteeing that a defective check is destroyed before a duplicate check is printed. A client terminal is connected to a check printer and a shredder. The client requests a check to be printed. If the printing is defective the check is submitted to the shredder, which destroys the check and enables the printer to print a duplicate. To the extent that the client has a more extensive data base than the printer, the destruction of the check is transmitted to the client as well as the printer. In this case it is the client that instructs the printer to print a duplicate. Finally, to the extent that a network is used for communication between the elements, encryption and passwords may be used for security.

Abstract: A method is described for printing a colorant controlled neutral black object in a bitmap-based digital color printing system. The method is useful in systems where the black colorant is not sufficiently opaque to hide non-neutral combinations of non-black colorants mixed into the black color. Black colors in a color printing system can be composed either of black colorant only or of black plus non-black colorants such as cyan, magenta, and yellow. If the non-black colorants are not mixed in nearly equal quantities, they will add hue to the black color. A sufficiently opaque black colorant can hide this objectionable non-black hue. However, in cases where the black colorant is not opaque enough, it is important to use equal or nearly equal combinations of cyan, magenta, and yellow so that little net hue will be introduced into the black color. Equally important in some printing systems is the ability to control the amount of total colorant used in forming a process black color.

Abstract: Printing hints can be efficiently compressed in a system using hierarchical compression (HVQ) by first using HVQ to generate compressed codewords, and then adding the printing hint to the codewords to generate an intermediate form of codeword, before sending this intermediate form to a pattern matching lossless compressor for final compression. Even though the same printing hint may be applied to a number of codewords, the overall compression will be affected very little by the addition of the printing hints since the hints are identical over a large number of codewords in series.

Abstract: A high speed image data interface between a print server containing a page description language decomposer and an interface card, and a printer containing a rendering card and a print engine, where the interface card is physically located in the printer case and is plugged into the backplane of the printer. The interface is synchronous and carries clock, page request, line request and reset signals from the renderer, and line valid, error and data signals from the interface card. Other communications between the printer and server are carried by a telephone line or local area network. The advantage of this arrangement is that the printer manufacturer can design the printer without having to design the interface card to match the server manufacturer's requirements.

Abstract: Many compression algorithms require the compressor to generate trees (tables) for encoding purposes. To generate the optimum tree for a set of Huffman symbols either takes too much time or requires too much hardware. This invention proposes to separate the symbols into groups according to the symbol's occurring frequency. With these groups of symbols available, subsequent code length assignment of these groups can be done without a complete sorting of all the symbols and their parents. During code length assignment, some relocation of individual symbols from one group to another can also be performed to optimize the Huffman table. In most of the cases this technique can achieve a compression ratio within 5% of the optimum Huffman table, while requiring less hardware or software overhead.

Abstract: A simple method of anti-aliasing for edges near the fast scan direction is to replace the pixels on both sides of the transition in a scan with pixels of varying intermediate color. Thus, if there is an edge between red and blue areas, instead of there being an abrupt change from red to blue at the edge, there will be a number of pixels that slowly vary from mostly red to mostly blue, which will tend to make the jagged edge less obvious.

Abstract: Every printing system has characteristic defects which detract from high quality printing. Xerographic printing systems show defects such as banding, mottled colors in large fill areas, trail-edge deletion and starvation where toner concentrations drop at certain color edges, misregistration, and so on. Ink jet printing systems can show ink bleeding, streaking in the direction of head movement, and so on. One approach to reducing predictable printer defects is to modify the digital data being sent to the printer to pre-compensate for the defect. One pre-compensation method identifies runs of color which meet the criteria likely to cause a printing defect and applies a function f(edge-distance, object-type) to such runs to modify them appropriately. However, if multiple defects are being corrected, an efficient method is needed to identify potential defects since a normal search procedure performed on a band of collected runs one at a time for each defect is time-consuming.

Abstract: A bitmap-based digital color printing method and system is described which automatically detects when a black object is to be printed and changes the Bit Block Transfer (BitBlt) method so that the black color becomes a mixture of black plus the background colorants, limited both by a clipping of one colorant against another and by an allowed maximum value for each remaining non-black separation. More specifically, the process reads the existing background color bits, does a first clip of one separation against another assuming that for correcting certain printing defects some separations are more important than others, and then does a second clip of remaining non-black separations to a pre-set maximum allowable amount. The result is an efficient way to control total colorant while allowing some separations precedence over others; with the result that the amount of colorant in one separation is dependent on or partially correlated with the amount of colorant in another.

Abstract: In the UNIX Operating System, modifying the kernel routine Physio, to enable a single system call to set up a number of concurrent direct memory access (DMA) channels between memory and the data buffers of a device. Many character device drivers use the UNIX Physio facility for I/O. The traditional implementation of Physio handles I/O in a serial manner by performing gather-write or scatter-read operations. This invention is an enhancement to Physio to support parallel I/O operations.

Abstract: A programmable direction control scheme for an efficiently wired array of like integrated circuit chips which is capable of producing a rightward or leftward sequence of designated interaction is described. The member chips are incorporated into a system by connecting their existing addressing, data, and clock pads onto a mutual bus. The chips are additionally chained together by their qualification pads so that they may be individually designated for interaction with the system, by way of sequential token passing. A direction control bit within a programmable configuration register is included on each member chip in lieu of a dedicated input. The configuration register is given free access irrespective of the designation status of its incorporating chip, and thus the direction control bits of all of the member chips of the array may be expediently programmed even when the elsewise process of sequencing through the chips would be paradoxically self obstructed by an initial directional chaos condition.