Patent US5493419A successfully refreshed from Google Patents.
US5493419A
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US
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Stack filters for 1-to-N bit image processing in electronic printers
Assignee: Xerox Corp
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Filing: 1995-07-14
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Granted: 1996-02-20
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Expires: 2015-07-14
Abstract
Abstract The present invention is a method and apparatus for the enhancement of 1 bit per pixel image signals to produce a multiple-bit per pixel form. A binary input image is passed through a plurality of filters to generate level slices. The filters are stack filters implemented as look-up table or template-based filters, morphological filters, or any similar binary-to-binary filters that could be used to generate level slices. Each of the N-1 filters is used to produce the slices, where N is the number of possible gray-scale levels desired in the output image. Once the slices are generated, the resulting binary image data therein is recombined, by adding or stacking, to produce the desired multiple-bit per pixel output.
Inventors
- 👤 Ronald E. Jodoin
- 👤 Robert P. Loce
- 👤 R. Victor Klassen
- 👤 Ying-wei Lin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 20:23
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/40075
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
174 words
A method for designing a stack filter, for enhancing a binary input image into a multiple-bit per pixel image, comprising the steps of: (a) obtaining a gray-scale image, wherein the image contains structures representative of structures appearing in documents to be enhanced from a binary to a multiple-bit per pixel gray-scale resolution; (b) thresholding the gray-scale image using a binary threshold level to produce a binary image; (c) thresholding the gray-scale image at second threshold, preferably not equal to the binary threshold, to produce a first level slice; (d) producing, as a function of the binary pixel levels in the binary image and the first level slice, a first difference image; and (e) generating, as a function of the first difference image and the binary image, a first level-slice filter having a plurality of templates which, upon receiving binary input signals in a pattern similar to that within a windowed subset of pixel locations within the binary image, will produce binary output signals equivalent to a corresponding pixel position in the first difference image.
Claim 2
Independent Claim
174 words
A method for designing a stack filter, for enhancing a binary input image into a multiple-bit per pixel image, comprising the steps of: (a) obtaining a gray-scale image, wherein the image contains structures representative of structures appearing in documents to be enhanced from a binary to a multiple-bit per pixel gray-scale resolution; (b) thresholding the gray-scale image using a binary threshold level to produce a binary image; (c) thresholding the gray-scale image at second threshold, preferably not equal to the binary threshold, to produce a first level slice; (d) producing, as a function of the binary pixel levels in the binary image and the first level slice, a first difference image; and (e) generating, as a function of the first difference image and the binary image, a first level-slice filter having a plurality of templates which, upon receiving binary input signals in a pattern similar to that within a windowed subset of pixel locations within the binary image, will produce binary output signals equivalent to a corresponding pixel position in the first difference image.
Claim 3
Dependent Claim
39 words
The method of claim 1, wherein the step of producing a first difference image includes XORing the binary pixel levels in the first level slice with the binary pixel levels in the binary image to produce the difference image.
Claim 4
Dependent Claim
189 words
The method of claim 1, further including the step of designing a second level-slice filter, said second level-slice filter designing step comprising the steps of: (a) thresholding the gray-scale image at a second threshold, preferably not equal to the binary threshold, to produce a second level slice; (b) applying the first level-slice filter to the binary image to produce a filtered difference image; (c) inverting the filtered difference image to produce an inverted image; (d) ANDing the binary pixel levels in the filtered difference image with the binary pixel levels in the binary image to produce a filtered level slice; (e) producing, as a function of the binary pixel levels in the second level slice and the filtered level slice, a second difference image; and (f) generating, as a function of the second difference image and the filtered level slice, a second level-slice filter having a plurality of templates which, upon receiving binary input signals in a pattern similar to that within a windowed subset of pixel locations within the second level slice, will produce binary output signals equivalent to a corresponding pixel position in the second difference image.
Claim 5
Dependent Claim
40 words
The method of claim 1, wherein the step of producing a second difference image includes XORing the binary pixel levels in the second level slice with the binary pixel levels in the filtered level slice to produce the difference image.
Claim 6
Dependent Claim
40 words
The method of claim 1, wherein the step of obtaining a gray-scale image includes the step of producing an idealized gray-scale image by averaging down a high addressability form of the gray-scale image and ORing it with a morphological skeleton.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-02-19 | 1999-08-21 | 2000-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-02-19 | 2003-08-21 | 2004-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-02-19 | 2007-08-21 | 2008-02-20 | $7700.00 | Window Closed / Lapsed |