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EP0441558A1
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Improvements relating to control data arrays
Assignee: Crosfield Electronics Ltd
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Filing: 1991-02-04
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Granted: —
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Expires: 2011-02-04
Abstract
Abstract Apparatus for generating an array of control data, the array having a number of pixels each of which corresponds to a respective pixel in an image, the apparatus comprising a first store (100) for storing the image data; a second store (17) for storing the control data; and a processor which, for each control data array pixel generates and stores in the second store (17) a control value in accordance with a predetermined algorithm which defines the control value as a function of the corresponding image pixel colour components and the corresponding colour component(s) of the target colours, wherein the generated control values can be ordered on a scale of at least three value classes.
Inventors
- 👤 Lindsay William Macdonald
- 👤 Richard Anthony Kirk
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 13:42
CPC Classifications
G; G06; G06T; G06T11/00; G06T11/10; H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/62
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
95 words
A method of generating an array of control data, the array having a number of pixels each of which corresponds to a respective pixel in an image, the method comprising selecting at least one target colour, and then for each control data array pixel generating a control value in accordance with a predetermined algorithm which defines the control value as a function of the corresponding image pixel colour components and the corresponding colour component(s) of the target colour(s), wherein the generated control values can be ordered on a scale of at least three value classes.
Claim 2
Dependent Claim
34 words
A method according to claim 1, wherein the predetermined algorithm defines the control value as representing a function of the Euclidean distance in colour space between the image pixel colour and the target colour.
Claim 3
Dependent Claim
74 words
A method according to claim 2, wherein the predetermined algorithm has the form D = √(a(C-C T )² + b(M-M T )² + c(Y-Y T )² + d(K-K T )²) where C T , M T , Y T , and K T are the colour component values of the target colour, C, M, Y, K, are the colour component values of the image pixel, and a, b, c, and d are weighting coefficients.
Claim 4
Dependent Claim
44 words
A method according to claim 1 or claim 2, wherein the predetermined algorithm has the form D = f(C,M) = a exp[-b(C-C T )²] exp[-c(M-M T )²] where a is a normalising factor and b, c govern the widths of the distributions for C,M.
Claim 5
Dependent Claim
47 words
A method according to claim 1 or claim 2, wherein the predetermined algorithm has the form f * (C,M) = f F (C,M) - f B (C,M) + f₀ where f F is the foreground function f B is the background function and f₀ is a constant
Claim 6
Independent Claim
63 words
A method according to any of the preceding claims, wherein the step of defining the target colour comprises specifying an area of interest within the image; constructing a histogram of pixel values within the specified area of interest and determining from the histogram the median and given percentile points for each colour component, and then providing the target colour weighting and spread coefficients.
Claim 7
Independent Claim
45 words
A method according to any of the preceding claims, further comprising a preliminary step in which the initial colour components defining the image in a first colour space are transformed into a second or subsequent colour space from which the control values can be determined.
Claim 8
Dependent Claim
52 words
A method according to claim 7, wherein the first colour space is transformed so that the colour components defining the central locus of the target colour range lie along the major axis of the second colour space, with the other two axes being perpendicular to the first axis and to each other.
Claim 9
Dependent Claim
112 words
Apparatus for generating an array of control data, the array having a number of pixels each of which corresponds to a respective pixel in an image, the apparatus comprising a first store for storing the image data; a second store for storing the control data; and processing means which, for each control data array pixel generates and stores in the second store a control value in accordance with a predetermined algorithm which defines the control value as a function of the corresponding image pixel colour components and the corresponding colour component(s) of the target colours, wherein the generated control values can be ordered on a scale of at least three value classes.
Claim 10
Dependent Claim
24 words
Apparatus according to claim 9, wherein the processing means is adapted to carry out a method according to any of claims 1 to 8.
Claim 11
Dependent Claim
98 words
Apparatus according to claim 10, when dependant on claim 3, wherein the processing means comprises 4 look-up tables each of which defines a function of the form X i = (i-Y T )²/N² where Y T is a target colour component value and N is a scaling coefficient chosen so that the required amount of sensitivity for that colour component is achieved, outputs from the look-up tables being fed to adders which generate the sum of the outputs, the output from the adders being fed to a fifth look-up table which reduces the accuracy back to eight bits.
References Cited (Backward Citations)
US4878178A
Cited
GB2208460A
Cited
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