Patent US5822467A successfully refreshed from Google Patents.
US5822467A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Sharpening filter for images with automatic adaptation to image type
Assignee: HP Inc
•
Filing: 1996-12-27
•
Granted: 1998-10-13
•
Expires: 2016-12-27
Abstract
Abstract A method of filtering images with a filter that is dependent on image type. For binary images, a fixed Laplacian filter is used for all pixels. For non-binary images, an automatic level-sensitive Laplacian filter is used. For non-binary images, Laplacian filter coefficients and normalization divisors are made a function of intensity on a pixel by pixel basis. Pixels indicating a high intensity may be greatly changed by neighboring pixels. Pixels indicating a low intensity receive relatively little or no filtering. In a specific example embodiment, the intensity range is divided to bands, with a different filter for each band. The resulting images are visually sharpened (edge enhanced) with very little impact in darker areas of the image.
Inventors
- 👤 Patricia D. Lopez
- 👤 Hal Hansen
- 👤 Jeffrey P. Lee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 18:58
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/40; H04N1/409; H04N1/4092
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
174 words
A method of spatially filtering an image, the image comprising an array of pixels, each pixel having a numerical value that is a measure of light intensity, the method comprising the following steps: (a) determining an image type; (b) applying a fixed spatial filter to the numerical values of the array of pixels when the image type is binary; and (c) applying a variable spatial filter to the numerical values of the array of pixels, when the image is other than binary, as follows: (c1) defining at least a first threshold range and a second threshold range; (c2) reading the numerical value of a pixel; (c3) applying the variable spatial filter, with a first central coefficient, to the numerical value of the pixel, when the numerical value is within the first threshold range; (c4) applying the variable spatial filter, with a second central coefficient, to the numerical value of the pixel, when the numerical value is within the second threshold range; and (c5) repeating steps (c2) through (c4) for all pixels in the array.
Claim 2
Independent Claim
174 words
A method of spatially filtering an image, the image comprising an array of pixels, each pixel having a numerical value that is a measure of light intensity, the method comprising the following steps: (a) determining an image type; (b) applying a fixed spatial filter to the numerical values of the array of pixels when the image type is binary; and (c) applying a variable spatial filter to the numerical values of the array of pixels, when the image is other than binary, as follows: (c1) defining at least a first threshold range and a second threshold range; (c2) reading the numerical value of a pixel; (c3) applying the variable spatial filter, with a first central coefficient, to the numerical value of the pixel, when the numerical value is within the first threshold range; (c4) applying the variable spatial filter, with a second central coefficient, to the numerical value of the pixel, when the numerical value is within the second threshold range; and (c5) repeating steps (c2) through (c4) for all pixels in the array.
Claim 3
Dependent Claim
19 words
The method of claim 1 where the fixed spatial filter and the variable spatial filter are both Laplacian filters.
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) | 2001-10-12 | 2002-04-13 | 2002-10-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-10-12 | 2006-04-13 | 2006-10-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-10-12 | 2010-04-13 | 2010-10-13 | $7700.00 | Window Closed / Lapsed |