EP0741492A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Selective colour correction applied to plurality of local color gamuts
Assignee: Agfa Gevaert NV
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Filing: 1996-04-03
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Granted: —
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Expires: 2016-04-03
Abstract
Abstract A method is described for selective colour correction of an original colour image. In one embodiment, a colour is selected by picking a coloured pixel from the colour image and a changed colour, having a restricted colour change, is associated with the selected colour. All original colours, situated within a local colour gamut, comprising the selected colour, undergo a colour modification according to the colour change. The effect of the modification decreases as the original colour reaches the boundary of the local colour gamut. The selected colour and changed colour may be defined in the native colour space, the local colour gamut is preferentially defined by an action radius related to a psychometric colour space. Two or more selective colour corrections may be combined by a weighted mean modification, by choosing for each colour change a weight value, which decreases as the selected colour is more different from the original colour.
Inventors
- 👤 Chris Tuijn
- 👤 Earle Stokes
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 19:24
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/62; H04N1/622
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
123 words
A method for selective correction of an original colour x → in an original colour image, comprising the steps of : - selecting at least two different colours µ → K , K=1,..N, N≥2; - defining for each selected colour µ → K a required colour change δ → K ; - defining for each selected colour µ → K a weighting function W K ( x → ) ; and, - applying a colour modification to said original colour x → , according to Σ K W K ( x → ) δ → K , K=1,..N is characterised in that W K ( µ → J ) = 0 if K≠J and W K ( µ → K ) = 1.
Claim 2
Dependent Claim
25 words
Method according to claim 1, wherein each weighting function obeys the following inequalities in its range of definition : 0≤W K ( x → )≤1.
Claim 3
Dependent Claim
38 words
Method according to any of claims 1 or 2, wherein the sum of all weighting functions, evaluated in any original colour x → , is not greater than one : Σ K W K ( x → )≤1.
Claim 4
Dependent Claim
27 words
Method according to any of claims 1 to 3, wherein each weighting function W K ( x → ) is defined by an extent and a shape.
Claim 5
Dependent Claim
38 words
Method according to claim 4, wherein said extent is defined by at least one action radius or by one or two action radii per coordinate axis, each action radius having said selected colour µ → K as origin.
Claim 6
Dependent Claim
22 words
Method according to claim 5, wherein said action radius is defined in a colour space having HSL, HSV or Lch coordinate axes.
Claim 7
Dependent Claim
23 words
Method according to any of claims 4 to 6, wherein the extent is set to comprise all colours contributing to said selected colour.
Claim 8
Dependent Claim
28 words
Method according to any of claims 4 to 7, wherein the shape of the weighting function W K ( x → ) is different for different coordinate axes.
Claim 9
Dependent Claim
24 words
Method according to any of claims 4 to 8, wherein said shape is based on the distribution of colours contributing to said selected colour.
Claim 10
Dependent Claim
62 words
Method according to any of claims 1 to 9, wherein a. said original colour x → , b. said selected colour µ → K , c. said required colour change δ → K , and/or d. said colour modification is defined in an RGB, Lab, CMY, CMYK, HiFi or named colour space, preferentially the same space for a, b, c and d.
Claim 11
Dependent Claim
28 words
Method according to any of claims 1 to 10, wherein said colour modification is combined with a global colour transformation, suitable for application to said original colour image.
Claim 12
Dependent Claim
18 words
Method according to claim 11, wherein said global colour transformation is defined on a sparse grid of colours.
Claim 13
Dependent Claim
19 words
Method according to any of claims 1 to 12, wherein said selected colour is obtained from said colour image.
Claim 14
Dependent Claim
42 words
Method according to any of claims 1 to 13, wherein said colour change δ → K is obtained from the difference between : - a desired colour selected on a reference colour image and - said selected colour µ → K .
Claim 15
Dependent Claim
68 words
Method according to any of claims 1 to 14, wherein said weighting function W K ( x → ) is not increasing as a distance D K between said original colour x → and said selected colour µ → K increases, as long as D K is smaller than a same distance between said selected colour µ → K and any different selected colour µ → J .
Claim 16
Dependent Claim
60 words
Method according to any of claims 1 to 15, wherein said weighting function W K ( x → ) decreases according to a linear, quadratic, cubic, gaussian or another function selected by an operator or is proportional to the inverse of a distance D K between said original colour x → and the corresponding selected colour µ → K .
References Cited (Backward Citations)
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