Adaptive thresholder
First Claim
1. Apparatus for adaptively thresholding the image pixels that comprise a video image signal on a pixel by pixel basis to distinguish white and black image areas in said video image signal, comprising, in combination:
- (a) white image signal parameter generating means responsive to transition of the video image signal from black to white to provide a white image signal parameter equal to larger of said video image signal and a preset minimum white signal;
(b) black image signal parameter generating means responsive to transition of the video image signal from white to black to provide a black image signal parameter equal to smaller of said video image signal and a preset maximum black signal;
(c) first means for combining said white and black image signal parameters to provide an offset parameter for the pixel being processed;
(d) second means for combining said offset parameter with the video image signal of at least one neighboring pixel to provide a threshold level for thresholding said pixel being processed; and
(e) thresholding means for thresholding said pixel with said threshold level.
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Accused Products
Abstract
An adaptive thresholder of the fractional average context type for processing image pixels in which an offset potential, which is used in conjunction with the image potentials of the nearest neighbor pixels to provide an updated threshold potential, is obtained on a pixel by pixel basis as a function of the pixel white peak and black valley potentials. The white peak and black valley potentials are compared with the image potential of each pixel being processed and with predetermined minimum white and maximum black potentials to provide updated white peak and black valley potentials for use in updating the offset potential during processing of each pixel.
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Citations
10 Claims
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1. Apparatus for adaptively thresholding the image pixels that comprise a video image signal on a pixel by pixel basis to distinguish white and black image areas in said video image signal, comprising, in combination:
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(a) white image signal parameter generating means responsive to transition of the video image signal from black to white to provide a white image signal parameter equal to larger of said video image signal and a preset minimum white signal; (b) black image signal parameter generating means responsive to transition of the video image signal from white to black to provide a black image signal parameter equal to smaller of said video image signal and a preset maximum black signal; (c) first means for combining said white and black image signal parameters to provide an offset parameter for the pixel being processed; (d) second means for combining said offset parameter with the video image signal of at least one neighboring pixel to provide a threshold level for thresholding said pixel being processed; and (e) thresholding means for thresholding said pixel with said threshold level. - View Dependent Claims (2, 3, 4)
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5. A process for adaptively thresholding the image pixels comprising a video image signal to distinguish white image areas from black image areas in said video image signal, comprising the steps of:
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(a) establishing a white image parameter equal to the larger of the instantaneous video image signal and a preset minimum white signal on transition of the video signal from black to white; (b) establishing a black image parameter equal to the smaller of the instantaneous video image signal and a preset minimum black signal on transition of the video signal from white to black; (c) combining said parameters in a predetermined relationship to provide an offset parameter for the pixel being processed; (d) combining said offset parameter with the video image signal from at least one neighboring pixel in a predetermined relationship to provide a threshold level for use in thresholding said pixel being processed; and (e) thresholding said pixel being processed against said threshold level. - View Dependent Claims (6, 7, 8, 9, 10)
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Specification