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Apparatus and method for performing resolution conversion on image data with auto correlation

  • US 5,282,051 A
  • Filed: 07/29/1991
  • Issued: 01/25/1994
  • Est. Priority Date: 07/29/1991
  • Status: Expired due to Term
First Claim
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1. A method for use in an electroreprographic machine of the type capable of manipulating digital images represented by a plurality of original image pixels, the electroreprographic machine having a buffering device for storing images and a raster output scanning device adapted to selectively discharge a photoreceptor member, the method including a step of developing an intensity signal for a selected output pixel in a set of output pixels from a plurality of input pixels in a set of input pixels, each of the plurality of input pixels having a corresponding intensity signal contributing to the intensity signal of the selected output pixel and being characterized by a center, the step of developing the intensity value of the selected output pixel comprising the steps of:

  • generating the intensity signals of the plurality of input pixels with an input signal device, the intensity signals being generated from an image with a constant resolution throughout;

    receiving the intensity signals of the plurality of input pixels from the input signal device and storing the intensity signals of the plurality of input pixels to the buffering device;

    mapping, in the buffering device, the set of output pixels to the set of input pixels so that each of the plurality of input pixels is adjacent the selected output pixel;

    reading the plurality of input pixels from the memory;

    determining a correlation value for each of the plurality of input pixels with a correlation function, the correlation function being based on a Gaussian correlation function, the Gaussian correlation function being characterized by the following expression;

    
    
    space="preserve" listing-type="equation">W(i,j)=C*(e.sup.-0.5(x(i)-X c.sup.)/σ

    x.sup.).spsp.2 *e.sup.-0.5 *.sup.(y(j)-Y c.sup.)/σ

    y.sup.).spsp.2);

    and where,C is a normalization constant,x(i) and y(i) are locations of the input pixels of the input image,X C and Y C are points about which a window of the input pixels is centered, and.sup.σ

    x and .sup.σ

    y are distances varying as a function of the perimeter of the window of the input pixel;

    summing the correlation values of the plurality of input pixels with the corresponding respective intensity signals of the plurality of input pixels to obtain the intensity signal of the selected output pixel, the selected output pixel being characterized by a resolution which is different than the resolution of the image from which the intensity signals of the plurality of input pixels were generated, the intensity signal of the selected output signal being employed to selectively control the raster output scanning device;

    designating a pivot point (XC, YC) for the selected output pixel; and

    disposing the centers of the plurality of input pixels substantially within a window centered about the pivot point.

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