Abstract: A symmetric key encryption system includes a printer or copier for performing decryption in two passes. During a first pass an encrypted image is decrypted to define a first partially decrypted image and during a second pass a complement of the encrypted image is decrypted to define a second partially decrypted image. The first partially decrypted image is formed when the encrypted image is rendered onto a first recording medium through a stencil. The stencil, which is a random arrangement of holes, is overlaid on the first recording medium to permit only selected portions of the encrypted image to be rendered on the recording medium. During the second pass, the complement of the encrypted image is rendered on a second recording medium through a complement of the stencil to yield the second partially decrypted image. Overlaying and aligning the first partially decrypted image and the second partially decrypted image finally decrypts the encrypted image.

Abstract: A system encodes a separate assist channel that carries only a small amount of additional information in a hardcopy document to compensate for failure of an OCR system to accurately reconstruct a scanned electronic version of the hardcopy document. The assist channel protects symbols printed on the hardcopy document by computing guard values that are derived from a hash of the character code of each character on the hardcopy document. Template match searches that are performed during decoding are limited to those interpretations that produce matching guard values.

Abstract: A digital image processing system for automatically segmenting a set of input image signals into a combination of predetermined classes of imagery, the set of input image signals forming part of a video image generated by an image input terminal. The system includes a classification circuit that receives the set of input image signals and classifies them as a ratio of the predetermined classes of imagery. A plurality of image processing circuits also receives the set of input image signals, each of which is adapted to process a unique class of imagery selected from the predetermined classes of imagery to generate a set of output image signals for that predetermined class of imagery.

Abstract: A method and apparatus are disclosed for locating and coloring true boundaries of image elements forming a color image defined with colors having one or more color separations. Once a boundary of an image element is located and determined to be a true boundary of the color image, the original color of the image element boundary is mapped to a solid color so that ragged edges created when rendering certain colors are minimized when reproducing. the color image element.

Abstract: A platenless book scanner with line buffering performs electronic perspective correction to account for rotation of the spine of a non-planar bound document relative to a reference line in a support plane of the platenless book scanner. A pre-scan of the non-planar bound document is performed to provide a geometrical contour map of the bound document. The geometrical contour map, which identifies displacement of the bound document from the support plane, is analyzed to calculate an angular offset between a spine of the bound document and the reference line in the support plane. The angular offset is used to identify a minimum number of scan line buffers for recording image data, from a set of scan line buffers. Once the minimum number of scan line buffers is filled with recorded image data, distortions caused by displacements of the non-planar bound document from the support plane and skew of the bound document relative to the reference line in the support plane are corrected.

Abstract: An overhead scanning system records pages from bound documents in an upright and open condition. The scanning system is defined with a general imaging geometry that makes the scanning system readily portable, and provides the scanning system with a variable imaging area. Once an operator defines an imaging area of an image acquisition system, the operator positions a light stripe projector to project across the imaging area. After recording calibration data, a perspective transform is provided by a perspective transform generator. In operation, a first image of the bound document having a light stripe projected there across is recorded by the image acquisition system. A page shape transform generator is then used to derive a page shape transform. Subsequently, a second image of the bound document is recorded without projecting a light stripe thereacross.

Abstract: A profile detector in a scanning system measures spacing of an original non-planar image from a reference image plane of the scanning system. The spacing is measured by projecting a spot of light, with a collimated light source, onto a scan line of the original non-planar image at an angle that is oblique with respect to the fast scan direction of the scanning system. A first photosensor converts optical information reflecting off of the original non-planar image at a first slow scan position into electrical profile data. A position along the fast scan direction is identified for the first slow scan position by locating the spot of light in the electrical profile data. The located position is compared with a pre-recorded position along the fast scan direction for the first slow scan position. The pre-recorded position defines a position where the first photosensor would have detected the spot of light if it reflected off of a planar image.

Abstract: A wedge shaped platen scanner sequentially records opposing pages of a bound document positioned thereon using a single imaging station. A mirror is positioned between the wedges of the platen. A controller positions the mirror in one of two operational positions. In the first operational position, the mirror is positioned so that light emitted by a lamp reflects off of the mirror and onto the single imaging station. In the second operational position, the mirror is moved out of the imaging station's optical path. In each operational position, the lamp sequentially illuminates an opposing page of the bound document with each of the three primary colors: red green, and blue. In both the first and the second operational positions, images of opposing pages of the bound document are focused with optics onto the imaging station. In one arrangement, the imaging station is a two-dimensional array of detectors which sense an image of a page of the bound document projected thereon.

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: 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: A digital halftoning system with balance error diffusion, converts a scanline at a time of an image from a first pixel density to a second pixel density, where the first pixel density is greater than the second pixel density. Quantization errors resulting from the conversion is dispersed to surrounding pixels, in a manner which is more symmetric than standard error diffusion techniques. Initially, errors are dispersed in a conventional manner during a first scanline pass or forward scanline pass of an image. Subsequently, errors are again dispersed during a second scanline pass or backwards scanline pass. The two pass error diffusion technique insures that error propagated throughout the image do not create or form correlated artifacts such as worms in the converted image.

Abstract: A method for a sender to automatically distribute information to a receiver on a network using devices (such as printers and facsimile machines) and communication channels (such as electronic mail) defined in a receiver profile. The receiver profile establishes the properties and mode for receipt of information for receivers on the network and the profile is published in a network repository for all network users or is accessible by selected groups or individuals on the network. Receivers have additional control over network senders by defining an information filter which further controls sender channel access (to a receiver) by defining some channels as having priority of access such as direct or delayed access, as well as selectively permitting senders to override the receiver profile. Consequently, receiver profiles provide a variable receiver definable link to senders using multiple forms of media as well as multiple hardware platforms and network configurations.

Abstract: A printing system for producing prints from a job represented by a stream of image data written in a page description language and having a token expressed as a plurality of bits. The stream of image data is generated by and transmitted from an image data source. The printing system comprises an input section, communicating with the image data source, for receiving the stream of image data. The input section includes an arrangement for reading a block of image data to determine the presence of the token in the block of image data. An area, communicating with the input section, is adapted to store the stream of image data. An arrangement, responsive to the reading means determining the presence of the token, is adapted to initiate a selected operation in the printing system after the input section receives a potion of the stream of image data. A parser, communicating with the storage area, is adapted to parse the stream of image data to separate the stream into a plurality of image-related components.

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: An image processing system with iterative error diffusion for halftoning a gray image made up of gray image signals to a binary image made up of binary image signals. The system uses two operational modes A and B to perform the error diffusion. During operational mode A, gray image signals stored in a scanline buffer are quantized to form binary image signals. Quantization errors resulting during operational mode A are distributed symmetrically to a selected set of error signals that have corresponding gray image signals in the scanline buffer and outside the scanline buffer. During a first iterative operation in mode B, error signals having corresponding gray image signals in the scanline buffer are dispersed symmetrically to the selected set of error signals.

Abstract: A representation of a shared structured container type data object with related data bases can be used to present information in a hierarchy or multi-level mode about the activities and status relating to the shared container type structured data object and related data bases and its content of a plurality of structured data objects as well as other information affecting or tracking the shared container type structured data object content in multi-levels. Further, user access control also provides exclusivity or privacy to invoked changes to parts of the shared container type structured data object and related data bases without interference from other users but with an indication to the other users of access control attributes thereby providing coordinated consistency among users relative to changes to all parts of the shared container type structured data object.

Abstract: In a method for converting from a first bitmap image resolution to a second bitmap resolution, be it interpolation (an increase in resolution) or decimation (a decrease in resolution) a bitmap image defined at resolution and density I.times.J.times.a is prefiltered as a first step to ensure the preservation of original image structure and compensate for device dependence of the input image, which is necessary in order to maintain the quality and sharpness of the original image. The filter may be selected from a variety of filter choices and may also perform pixel interpolation or decimation depending on the input source. As a second step, unquantized scaling of a prefiltered image (K.times.L.times.b) is performed using an f.times.g pixel window to identify a set of neighboring input pixels surrounding a single output pixel. The window contributes input pixel density information to generate a scaled gray output pixel.

Abstract: There is provided a method to convert gray level image data from image input terminals, into binary data for high-addressability image output terminals. High addressability output terminals such as printers increase their virtual resolution in the fast scan direction in order to achieve a higher effective printing resolution. For example, one pixel in the slow scan direction divided into eight pixels in the fast scan direction, improves a printer's actual resolution from n spots.times.m spots per unit area to (8 * n) spots.times.m spots per unit area. Gray level input data representing pixel data from image input terminals such as scanners is encoded by either an analog signal or a quantized digital signal with a large number of levels (e.g. 256 levels). Binary output data has pixels with either a value of one or zero or a much smaller number of gray levels compared to digital input signals.