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US6438264B1
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Method for compensating image color when adjusting the contrast of a digital color image
Assignee: Monument Peak Ventures LLC
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Filing: 1998-12-31
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Granted: 2002-08-20
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Expires: 2018-12-31
Abstract
Abstract A method of adjustment of the color saturation characteristics of a digital color image is performed in order to compensate for an applied luminance tone scale function. This method comprises of the steps of receiving a tone scale function, calculating a local slope of the tone scale function for each pixel of the digital color image, calculating a color saturation signal from the digital color image, and adjusting the color saturation signal of the digital color image for each of the pixels based on the calculated local slope.
Inventors
- 👤 Andrew C. Gallagher
- 👤 Edward B. Gindele
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:10
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/57; H04N9/00; H04N9/64; H04N9/643
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
86 words
A method for processing a digital color image having a plurality of pixels, the method comprising the steps of: (a) receiving a tone scale function; (b) calculating a local slope of the tone scale function for each pixel of the digital color image based on a ratio calculation evaluated for each pixel; (c) calculating a color saturation signal from the digital color image, and (d) adjusting the color saturation signal of the digital color image for each of the pixels based on the calculated local slope.
Claim 2
Independent Claim
86 words
A method for processing a digital color image having a plurality of pixels, the method comprising the steps of: (a) receiving a tone scale function; (b) calculating a local slope of the tone scale function for each pixel of the digital color image based on a ratio calculation evaluated for each pixel; (c) calculating a color saturation signal from the digital color image, and (d) adjusting the color saturation signal of the digital color image for each of the pixels based on the calculated local slope.
Claim 3
Dependent Claim
32 words
The method as in claim 1 further comprising the steps of: transforming the digital color image into luminance and chrominance color signals; and modifying the luminance signal by the tone scale function.
Claim 4
Dependent Claim
97 words
The method as in claim 1 , wherein the step of calculating the local slope of the tone scale function includes: determining a maximum and minimum value at a pixel location; determining an output of the tone scale function for both the maximum and minimum values; determining a difference of the maximum and minimum values; determining the difference of the output maximum and the output minimum values; and calculating a ratio of the difference of the output of the tone scale function for the maximum and minimum values to the difference of the maximum and minimum values.
Claim 5
Dependent Claim
116 words
The method as in claim 1 , wherein the step of calculating the local slope of the tone scale function includes determining a luminance value at a pixel location; selecting an arbitrary small integer delta value; determining an output of the tone scale function for both the sum of the luminance value and the delta value, and the sum of the luminance value and the negative of the delta value; determining the difference of the output of the sum of the luminance value and the delta value and the output of the sum of the luminance value and the negative of the delta value; and calculating a ratio of the difference to twice the delta value.
Claim 6
Dependent Claim
27 words
The method as in claim 1 further comprising the step of providing a color position weight based upon the pixel value of the original digital color image.
Claim 7
Dependent Claim
34 words
The method as in claim 5 , wherein the step of adjusting the color saturation signal of the digital color image is dependent upon both the calculated local slope and the color position weight.
Claim 8
Dependent Claim
49 words
The method as in claim 1 , wherein the step of adjusting the color saturation signal is further comprised of: calculating one or more color difference signals; and adjusting the color difference signals of the digital color image for each of the pixels based on the calculated local slope.
Claim 9
Dependent Claim
32 words
The method as in claim 7 further comprising the steps of: transforming the digital color image into luminance and chrominance color signals; and modifying the luminance signal by the tone scale function.
Claim 10
Dependent Claim
98 words
The method as in claim 7 , further wherein the step of calculating the local slope of the tone scale function includes: determining a maximum and minimum value at a pixel location; determining an output of the tone scale function for both the maximum and minimum values; determining a difference of the maximum and minimum values; determining the difference of the output maximum and the output minimum values; and calculating a ratio of the difference of the output of the tone scale function for the maximum and minimum values to the difference of the maximum and minimum values.
Claim 11
Dependent Claim
116 words
The method as in claim 7 , wherein the step of calculating the local slope of the tone scale function includes: determining a luminance value at a pixel location; selecting an arbitrary small integer delta value; determining an output of the tone scale function for both the sum of the luminance value and the delta value, and the sum of the luminance value and the negative of the delta value; determining the difference of the output of the sum of the luminance value and the delta value and the output of the sum of the luminance value and the negative of the delta value; and calculating a ratio of the difference to twice the delta value.
Claim 12
Dependent Claim
27 words
The method as in claim 7 further comprising the step of providing a color position weight based upon the pixel value of the original digital color image.
Claim 13
Dependent Claim
34 words
The method as in claim 11 , wherein the step of adjusting the color saturation signal of the digital color image is dependent upon both the calculated local slope and the color position weight.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2005-08-19 | 2006-02-18 | 2006-08-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2009-08-19 | 2010-02-18 | 2010-08-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2013-08-19 | 2014-02-18 | 2014-08-20 | $7700.00 | Window Closed / Lapsed |