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.

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 sep...

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 se...

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...

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.

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...

A method of decoding Huffman-encoded words at the rate of one per clock cycle. The encoded words are formed into two strings of bits, one for odd numbered code and one for even numbered code, and two decoders in parallel are used, each first shifting in a number of coded bits during a first clock period, and converting the Huffman code to data on a second clock period. The two parallel decoders are timed so that the shift cycle of one decoder occurs at the same time as the conversion cycle of th...

A circuit for decoding one non-zero JPEG encoded pixel per clock cycle, the coded word being of variable length. For a pixel with leading zeros, a two stage pipeline is used, the first stage having one adder for calculating an delta value between the smallest number the variable length portion could be and the actual value, the second stage being an adder for adding the delta value to a base address to generate an address for a look up table, the output being the decoded value. This takes two cl...

A method for increasing the speed of color conversion from a plurality of color spaces to a single color space by reducing the number of color pixels by a factor of two prior to the color conversion step. This pixel reduction constitutes a lossy data compression scheme which takes advantage of the advance knowledge that the pixels will later undergo anti-aliasing by averaging subsequent to the color conversion. First the pixels are grouped into pairs, and one pixel of each pair is eliminated to ...

Two sided electric paper that can be written onto on both sides by having a layer of conductive material between two sheets of electric paper. The electric paper is made of small balls encased in a liquid so that they are free to rotate, and then suspended in a solid substrate. Each ball has two hemispheres, one white and one black, each hemisphere also having a different electrical quality. Thus, in an electric field, the balls can be made to rotate to create an image of black and white areas. ...