EP1017241A2
Expired / Lapsed
EP
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A method for compensating image color when adjusting the contrast of a digital color image
Assignee: Eastman Kodak Co
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Filing: 1999-12-01
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Granted: —
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Expires: 2019-12-01
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 Charles Gallagher
- 👤 Edward Brooks Gindele
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 11:00
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/57; H04N9/00; H04N9/64; H04N9/643
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
77 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; (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
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 3
Dependent Claim
96 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 4
Dependent Claim
115 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 5
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 6
Dependent Claim
33 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 7
Dependent Claim
48 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 8
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 9
Dependent Claim
97 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 10
Dependent Claim
115 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.
References Cited (Backward Citations)
No citation records indexed.
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