Patents Represented by Attorney, Agent or Law Firm M. J. Nickerson
  • Patent number: 6252679
    Abstract: A method and system of designing a digital halftoning screen for forming images on output sheets according to a set of image signals. The method generates a halftone line screen having multiple levels, each level having multiple line segments, each line segment having an equal pre-determined number of elements. The method stochastically assigns threshold values to pixels corresponding to a first element within the multiple line segments of a first level and assigns a same threshold value to a pixel corresponding to a single level to create a first element stochastic fill sequence. The method then assigns threshold values to pixels corresponding to a first element within the multiple line segments of the remaining levels of the halftone line screen according to the first element stochastic fill sequence.
    Type: Grant
    Filed: November 18, 1998
    Date of Patent: June 26, 2001
    Assignee: Xerox Corporation
    Inventor: Shen-ge Wang
  • Patent number: 6233360
    Abstract: A method and system implements a high addressability characteristic into an error diffusion process. A histogram of the image is generated and the actual background and black reference values are determined. A gray level value representing a pixel is received. The gray level value has a first resolution which corresponds to an original input resolution. The gray level value is interpolated to generate subpixel gray level values which correspond to a second resolution. The second resolution is higher than the first resolution and corresponds to the high addressability characteristic. A threshold circuit thresholds the interpolated gray level value and generates an error value as a result of the threshold using the determined background and black reference values. The error value has a resolution corresponding to the first resolution. A portion of the error value is diffused to adjacent pixels on a next scanline.
    Type: Grant
    Filed: September 24, 1996
    Date of Patent: May 15, 2001
    Assignee: Xerox Corporation
    Inventors: David J. Metcalfe, Roger L. Triplett, Xiao-fan Feng, John T. Newell
  • Patent number: 6219450
    Abstract: A method detects if an image is compressed. The method determines a block grid within the image and establishes blocks from the determined grid. The method then computes differences between samples inside the established blocks and differences between samples across the established blocks. The method determines that the image is compressed based on characteristics derived from statistics of the computed differences.
    Type: Grant
    Filed: November 13, 1998
    Date of Patent: April 17, 2001
    Assignee: Xerox Corporation
    Inventor: Ricardo L. de Queiroz
  • Patent number: 6195457
    Abstract: A method detects if an image is compressed. The method determines a block grid within the image and establishes blocks from the determined grid. The method then computes differences between samples inside the established blocks and differences between samples across the established blocks. The method determines that the image is compressed based on characteristics derived from statistics of the computed differences.
    Type: Grant
    Filed: November 13, 1998
    Date of Patent: February 27, 2001
    Assignee: Xerox Corporation
    Inventor: Ricardo L. de Queiroz