Image processor and method for processing pixel data
First Claim
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1. An image processor for processing pixel data defining an image, said pixel data defining an intensity for each of a plurality of pixels having a plurality of gradiations between a predetermined minimum and maximum, said image processor including image processing logic comprising:
- means for determining the intensity difference between adjacent pixels of said image;
means for comparing said intensity difference with a predetermined nonzero threshold that is less than the difference between said predetermined minimum and said predetermined maximum to detect stepped intensity transitions characteristic of staircase aliasing in the image;
means for determining a stepped intensity range indicating the range of pixels through which said intensity remains essentially constant;
means for determining an antialiased pixel value for each of said range of pixels, said antialiased pixel value being a function of said range and said adjacent pixel intensities; and
means for producing an output image including said antialiased pixel values on the detected stepped transitions.
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Abstract
An image processor has image processing logic for detecting pixel data representing stepped chrominance or luminance transitions characteristic of staircase aliasing in a source image and for producing an output image including selective antialiasing on the detected stepped transitions. The image processing logic operates as a post processor, but is able to give much better results than conventional convolution filtering.
36 Citations
20 Claims
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1. An image processor for processing pixel data defining an image, said pixel data defining an intensity for each of a plurality of pixels having a plurality of gradiations between a predetermined minimum and maximum, said image processor including image processing logic comprising:
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means for determining the intensity difference between adjacent pixels of said image; means for comparing said intensity difference with a predetermined nonzero threshold that is less than the difference between said predetermined minimum and said predetermined maximum to detect stepped intensity transitions characteristic of staircase aliasing in the image; means for determining a stepped intensity range indicating the range of pixels through which said intensity remains essentially constant; means for determining an antialiased pixel value for each of said range of pixels, said antialiased pixel value being a function of said range and said adjacent pixel intensities; and means for producing an output image including said antialiased pixel values on the detected stepped transitions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. In a graphics system in which a two-dimensional image consisting of rows and columns of pixels is generated for display by a raster scan device, said image being represented by pixel data defining an intensity for each of said pixels having a plurality of gradiations between a predetermined minimum and maximum, a method for processing said pixel data comprising the steps of:
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determining the intensity differences between adjacent pixels of said image; comparing said intensity differences with a predetermined nonzero threshold that is less than the difference between said predetermined minimum and said predetermined maximum to detect stepped transitions characteristic of staircase aliasing in said image; determining a stepped intensity range indicating the range of pixels through which said intensity remains essentially constant; determining an antialiased pixel value for each of said range of pixels, said antialiased pixel value being a function of said range and said adjacent pixel intensities; and modifying said pixel data for pixels along said detected transitions to product an output image including said antialiased pixel values along said transitions. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification