Abstract: A color image is reproduced with a set of colors wherein each color is defined in terms of a pattern block. Pattern blocks include a pattern using the color to be reproduced and white in density-related combinations so that the luminance difference between the color and white can be retained when copied or printed with a black printer. The patterns add among colors thus allowing combination colors to be represented in terms of added patterns of colors represented in black as distinct patterns.

Abstract: A decoding technique that allows a compressed image to be constructed into a full color page for printing is disclosed. The technique employs a split-level image buffer. The image is divided into small blocks which can be individually compressed and decompressed, allowing the image to be constructed and modified in compressed form. Each small block is examined and labeled as being encoded from one of a plurality of predefined encoding processes. Each block is then decoded in response to the encoding processes in which the block was labeled as being.

Abstract: A method of encoding an image at full resolution for storing in a reduced image buffer for subsequent decoding and printing by a marking device, the method including the steps of dividing the image into a plurality of blocks wherein each block is comprised of a plurality of pixels. The step of identifying a number of color regions present in each of the plurality of blocks. The step of selecting a predefined encoding process from a plurality of predefined encoding processes for each of the plurality of blocks according to the number of color regions present in each of the plurality of block. And, the step of storing the encoded plurality of blocks in the reduced image buffer for subsequent decoding and printing by the marking device.

Abstract: A method of processing images preparatory to printing in a color printer adapted to printing serial color separations, that when superposed form the final color image, in which separation color images are received for printing defined by continuous tone separation signals, which are color corrected and halftoned preparatory to printing the color image. The received continuous tone separation image signals are used to derive an estimate of marking material coverage. The marking material coverage estimate is subsequently used in association with random number generation to turn OFF otherwise ON pixels in each separation as the separation is printed for the reduction of marking material coverage.

Abstract: A method for selecting an optimum encoding process for a block of pixels from a plurality of predefined encoding processes, including the step of identifying a number of color regions present in the block. The step of determining geometric relationships between the color regions in the block. And, the step of selecting an encoding process from a plurality of encoding processes in response to the identifying step and the determining step.

Abstract: Halftone screens are generated for each separation in accordance with the goal of avoiding overlapping whenever possible. Initially, the black separation is halftoned, generating a dot pattern with a number of ON pixels and OFF pixels in accordance with the area density of the black separation. Next, a first color separation is halftoned, setting a number of the previous OFF pixels to ON. Then, if any white pixels remain, the second color separation is halftoned, setting a number of the previously OFF pixels to ON. If during the processing of the second and third separations, it is determined that no OFF pixels exist to be turned ON, a second layer of color is started, respectively superimposed over the first layer. The third color separation is halftoned in reverse fill-in order, setting a number of the previous OFF pixels to ON. Each layer is started and arranged so that the additional colors forming the dot pattern are not placed on any black areas.

Abstract: A method and apparatus for operating an ink jet printer of the type which prints a swath of the image at a time with each transit across a sheet. An image portion corresponding to a potential swath is examined, particularly determining for each column whether any breaks occur at any point in a relevant portion of the column. If no breaks are found in any single column, the swath and the next swath are printed unidirectionally. However, if breaks are found at acceptable locations in every column, the swath and the next swath can be printed bidirectionally. For each column, the pattern of bits in the column above the break points in each column are directed to the print buffer to be printed in the first swath, while the remaining bits will be sent to a buffer for the next swath. The distance for the next paper advance is calculated, considering the locations of the breakpoints.

Abstract: This invention relates to coil assemblies and in particular, but not exclusively, to such assemblies for acoustic transducers. Thus a transducer 10 includes a case 11 in which is located a coil 16 mounted on a flexi-circuit, which locates the coil 16 for its assembly handling and which allows various configurations within the case 11. A method of winding the coil 16 and mounting it on the carrier 17 is also described.

Abstract: A method for forming a plurality of halftone density patterns in an image processing system. Each density pattern is formed using a halftone cell that is incrementally grown according to a pixel growth pattern that is defined by the position of each threshold value in the halftone cell. The plurality of halftone density patterns are formed in accordance with at least two tests, one for an upper gray density boundary U(d) and one for a lower gray density boundary L(d). The two gray density boundary tests enables different density patterns having the same number of pixels but different densities to be formed by altering the growth pattern of the halftone cell. The two boundaries U(d) and L(d) define a valid range for each gray density threshold in a halftone cell. The defined range insures that pixels are added or removed along the pixel growth pattern of the halftone cell, thereby altering the perceived density of halftone density patterns having an equal number of pixels.

Abstract: A method and apparatus is disclosed for mapping original colors of image elements forming a color image to colors that appear solid when reproduced on a color printer. The original color and the solid color of each image element may be defined by a subtractive mixture of cyan, magenta and yellow colorants. The method first determines whether the original color of each image element is a light color surrounded by a dark background color, or a dark color surrounded by a light background color. Subsequently, the cyan and magenta colorants of each original color determined to be a light color surrounded by a dark background color are minimized; and one of the cyan or magenta colorants for each color determined to be dark and surrounded by a light background color is maximized. Consequently, image elements having colors defined by the mapping appear solid when reproduced by the color printer.

Abstract: A method and apparatus for achieving an ultra-small or compressed image buffer images at half the resolution and then scales by two to achieve the device resolution. Acceptable quality can be maintained by identifying edge and interior portions of the page image and using this information to scale intelligently. A split-level frame buffer provides this identification of the image components. Further, an extension of block-truncation coding can be used with the split-level frame buffer to provide up to a 16 to 1 compression for an overall compression of up to 64 to 1. Actual techniques to scale these encodings are described along with new encodings for graphics and text designed this high compression of the image.

Abstract: Input device signals R.sub.s, G.sub.s, B.sub.s generated by an image input terminal are converted to colorimetric values R.sub.c, G.sub.c, B.sub.c. The colorimetric values processed by an image processing unit to generate address entries to a lookup table which stores a set of transform coefficients with which the R.sub.c, G.sub.c, B.sub.c values may be processed to convert them to C.sub.x, M.sub.x, Y.sub.x, K.sub.x colorant signals or any multi-dimensional output color space, which include but are not limited to CMYK or spectral data. Values which are not directly mapped from the table are determined using tetrahedral interpolation over a hexagonal lattice. The hexagonal lattice is formed by offsetting by a half unit every other row of one of its dimensions relative to another dimension. The offset provides closer packing of sample points that define more regular tetrahedrons to reduce relative interpolation errors.

Abstract: An image processing system for preparing a document image for printing, each discrete area or pixel in the image described by a signal having a number of possible states greater than can be rendered by a selected printer. In such a system a screening pattern is used which distributes screen values through the image in accordance with the pattern of a space filling curve. Each signal is thresholded against a threshold determined by such ordering and output a signal renderable by the selected printer. A straight forward function relates threshold value in a screen matrix of values and the length of a space filling curve at any point in an image. The nature of certain space filling curves, allows the generation of two reasonably sized lookup tables providing the length of the curve at any point on the page.

Abstract: A decomposing apparatus is provided for use in a printing machine of the type adapted to receive a first set of information written in a printer page description language and a second set of information written in a printer page description language. The decomposing apparatus preferably includes: an arrangement for parsing the first set of information into a first set of image related components during a first time interval and the second set of information into a second set of image related components during a second time interval; and, an arrangement for performing image related operations on selected components of the first set of image related components, the image related operations being performed on the first set of image related components during the second interval so that the image related operations can be performed on the first set of image related components substantially concurrently with the second set of information being parsed.

Abstract: Halftone screens are generated for each separation in accordance with the goal of avoiding overlapping whenever possible. Initially, the black separation is halftoned, generating a dot with a number of ON pixels and OFF pixels in accordance with the area density of the black separation. Next, a first color separation is halftoned, setting a number of the previous OFF pixels to ON. Then, if any white pixels remain, the second color separation is halftoned, setting a number of the previously OFF pixels to ON. After the second color separation is halftoned, if any OFF pixels remain, the third color separation is halftoned, setting a number of the previous OFF pixels to ON. If during the processing of the second and third separations, it is determined that no OFF pixels exist to be turned ON, second and third layers of color is started, respectively superimposed over the first layer and then, if required, superimposed over the second layer.

Abstract: A thermal ink-jet printer in which two parallel linear arrays of ejectors are disposed on a reciprocating carriage. The linear arrays are subdivided into sections, the ejectors in each section being adapted to emit ink of a preselected primary color. The linear arrays overlap to optimize a trade-off between speeds of monochrome and full-color operation.

Abstract: Elements of a three-dimensional object having a plurality of flat polygonal surfaces are constructed by providing a visual model of the object and constructing a graph from the visual model. The graph illustrates a plurality of nodes connected by lines. Each node represents one of the polygonal surfaces, and each line connecting the nodes corresponds to an edge of the visual model located between corresponding polygonal surfaces. One of the nodes is selected as a starting node, and the graph is traversed beginning at the starting node. The traversal continues by successively traveling from previously selected nodes to previously unselected nodes along the lines without selecting any node more than once. The elements are constructed by drawing a corresponding polygon for each node as the nodes are selected.

Abstract: A method for calibrating a printer determines a tone reproduction curve for the printer. A plurality of bands of different accurate gray level standards and a corresponding number of smoothly increasing sequences of gray level specifications for the printer are printed adjacent to one another. Adjacent bands and sequences are compared, and a point along each band where the band appears equal to the adjacent gray level specification sequence is determined. The points are interpolated and the interpolated values are used to form a tone reproduction curve for the printer. The tone reproduction curve, representing the correspondence between the gray level specification of the printer and the actual gray levels produced by the printer, can then be used to calibrate the printer. The calibrating method can also be used for color printers.

Abstract: A method for improving the quality of full-color images is disclosed. An original image is divided into a plurality of pixels. A neutral intensity value is determined for each pixel. A desired black-color intensity value is determined from the neutral intensity value. A printer-producible black value is determined from the desired value. The printer-producible black-color intensity value is used to rescale the original color intensity values of the pixels. The rescaled color intensity values are used to generate output color intensity values. The output image comprising the output color intensity values and the printer-producible black-color intensity value may then be converted to a continuously varying or halftone output image and output to an image output apparatus.

Abstract: Conversion from odd to non-zero winding number convention for representation of polygons in a graphics system comprises entry of a polygon in a frame buffer using distinguished states. Special scanlines are determined and marked. Special scanlines are those of relative maxima and minima, and those bordering regions where the polygon touches itself. Each of the special scanlines is examined and entries for the polygon on a scanline are marked odd or even (down or up). The polygon is drawn for a second time. During this drawing, the distinguished state (temporary) entered on the first pass is replaced by a down or up state. The state entered is the current direction value, except for entries on special scanlines. For special scanlines the state entered is given by the marked entry in the frame buffer. This value also becomes the current direction value for subsequent entries.