EP0709806A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Color correction device and color correction method
Assignee: Panasonic Holdings Corp
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Filing: 1995-10-24
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Granted: —
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Expires: 2015-10-24
Abstract
Abstract A color correction device for correcting colors in a color image, comprising: standard point registration means for registering coordinates of a standard point on a color space for at least one color to be used as a standard for color correction; object point registration means for registering coordinates of an object point on the color space which corresponds to a standard point and which is a desired color after color correction; and coordinate conversion means for determining a mapping function based on the standard point and the object point, and for generating a corrected color image by using the mapping function to convert pre-correction points on the color space which are equivalent to a color of each pixel in an inputted pre-correction image. By means of the construction described above, all of the colors in a color space can be converted based on at least one pair of standard point and object point. As a result, precise color correction can be easily achieved.
Inventors
- 👤 Jun Ikeda
- 👤 Tsuyoshi Hirashima
- 👤 Tadanori Tezuka
- 👤 Hitoshi Fujimoto
- 👤 Yuji Shimizu
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 12:53
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/62; H04N1/622
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
138 words
A color correction device for correcting colors in a color image, comprising: standard point registration means for registering coordinates in a color space of at least one standard point, the color space having axes for specifying colors and a standard point representing a color to be used as a standard for color correction; object point registration means for registering coordinates in the color space of an object point for each standard point, each object point representing a desired color to be achieved by color correction of a standard point; and coordinate conversion means for determining a mapping function which maps each standard point to a corresponding object point and which can be used for mapping any arbitrary point in the color space, and for generating a corrected color image from an inputted pre-correction image using the mapping function.
Claim 2
Dependent Claim
53 words
The color correction device of Claim 1, wherein the mapping function is a function where an effect of a standard point on an amount which an arbitrary point in the pre-correction image is moved during mapping decreases as a distance in the color space from said pre-correction point to said standard point increases.
Claim 3
Dependent Claim
140 words
The color correction device of Claim 2, wherein the coordinate conversion means includes: standard movement amount calculation means for calculating a standard movement amount for each standard point, said standard movement amount being a standard value used in determining an amount which a point in the pre-correction image is moved during mapping; first weighting coefficient calculation means for calculating a weighting coefficient which corresponds to a distance from a standard point to a pre-correction point, using a fixed weighting coefficient function which has the weighting coefficient decrease uniformly with said distance; summing means for summing products of a standard movement amount and the weighting coefficient, for every standard point; and color image generation means for adding a value calculated by the summing means to the coordinates of the pre-correction point so as to generate a color in a corrected image.
Claim 4
Dependent Claim
159 words
The color correction device of Claim 3, wherein the standard movement amount calculation means includes: correction amount calculation means for calculating a difference (hereinafter, correction amount) in the coordinates between a standard point and a corresponding object point, for every standard point; distance calculation means for calculating a distance between all possible combinations of two standard points, including combinations where there is duplication of a same standard point; second weighting coefficient calculation means for using the weighting coefficient function to calculate a weighting coefficient for each distance calculated by the distance calculation means; inverse matrix generation means for generating an inverse matrix of a matrix, wherein weighting coefficients calculated by the second weighting coefficient calculation means are elements in said matrix; and matrix multiplication means for multiplying the inverse matrix generated by the inverse matrix generation means by the correction amounts and for setting multiplication results as the standard movement amount, wherein there is a plurality of standard points.
Claim 5
Dependent Claim
38 words
The color correction device of Claim 1, wherein the mapping function is a function which performs interpolation and extrapolation for any arbitrary point in the color space setting all of the standard points and object points as standards.
Claim 6
Dependent Claim
61 words
The color correction device of Claim 5, wherein the coordinate conversion means includes: distance determination means for comparing a distance on the color space between two standard points with a fixed threshold value; and calculation order determination means for determining object points to be simultaneously used when executing interpolation and extrapolation, based on a comparison result for the distance determination means.
Claim 7
Dependent Claim
77 words
The color correction device of Claim 1, wherein the coordinate conversion means includes: LUT storage means for storing a look up table (hereinafter, LUT) made up corresponding sets of coordinates for a plurality of predetermined points in the color space and coordinates of points achieved by mapping said points using the mapping function; and LUT reference means for retrieving, once a pre-correction color image has been inputted, post-correction points corresponding to pre-correction points in the color image.
Claim 8
Dependent Claim
35 words
The color correction device of Claim 7, wherein the LUT reference means generates a corrected color image by retrieving a predetermined number of points in the LUT and executing an interpolation calculation between said points.
Claim 9
Dependent Claim
152 words
The color correction device of Claim 1, wherein the coordinate conversion means includes: temporary storage means for storing coordinates obtained by conversion using the mapping function corresponded to points before conversion; hit detection means for detecting, once a pre-correction color image is inputted, whether pre-correction points in the pre-correction color image are being stored by the temporary storage means; temporary storage retrieval means for retrieving, when the hit detection means detects that the pre-correction points are being stored, converted points corresponding to the pre-conversion points from the temporary storage means, thereby generating the corrected color image; and temporary storage writing means for writing, when the hit detection means detects that the pre-correction points are not being stored, points which are converted according to the mapping function and corresponding pre-conversion points into the temporary storage means, as well as generating the points of the corrected color image from the points which are converted.
Claim 10
Dependent Claim
72 words
The color correction device of Claim 9, wherein the coordinate conversion means further includes: temporary storage updating means for detecting whether there is free space for storing in the temporary storage means and, when a detection result is that there is no space for storing, for ensuring there is sufficient space for the temporary storage writing means to write by deleting a content at an appropriate position in the temporary storage means.
Claim 11
Dependent Claim
45 words
The color correction device of Claim 10, wherein the temporary storage means stores coordinates of post-conversion points at blocks corresponded to coordinates of pre-conversion points, and the hit detection means detects whether a pre-conversion point is stored by the temporary storage means using the blocks.
Claim 12
Dependent Claim
51 words
The color correction device of Claim 1, further including correction standard indication means for receiving an indication of any arbitrary point in the color space and for storing said point as the standard point in the standard point registration means and as the object point in the object point registration means.
Claim 13
Dependent Claim
80 words
The color correction device of Claim 12, wherein the correction standard indication means includes: display means; input operation means for receiving an indication from the user; and display control means for displaying an operation image on the display means, for determining the standard point and the object point based on an indication received via the input operation means, and for storing the standard point in the standard point registration means and the object point in the object point registration means.
Claim 14
Dependent Claim
128 words
The color correction device of Claim 13, wherein the display control means includes: image display means for displaying the pre-correction color image and the corrected color image on the display means; and storage means for obtaining, when a pixel in the pre-correction color image is indicated by the input operation means, coordinates of said pixel as the standard point and an object point, for obtaining, when a pixel in the corrected color image is indicated by the input operation means, coordinates of said pixel as an object point, and coordinates of a pixel in a corresponding position in the pre-correction color image as the standard point, and for storing the standard point in the standard point registration means and the object point in the object point registration means.
Claim 15
Dependent Claim
42 words
The color correction device of Claim 13, wherein the display control means includes correction standard display means for displaying every pairing of standard point and object point indicated by the input indication means arranged into a same window on the display means.
Claim 16
Dependent Claim
64 words
The color correction device of Claim 15, wherein the display control means includes object point conversion means for setting, once a pairing of standard point and object point displayed in the same window have been selected by means of the input indication means, the object point in the pairing to be edited, and obtaining a newly indicated object point as a valid object point.
Claim 17
Dependent Claim
53 words
The color correction device of Claim 16, wherein the object point conversion means displays at least one of sliders, sample colors, and numerical values in order to correct values of the object point in each axis of the color space and receives an editing based on an indication by the input indication means.
Claim 18
Dependent Claim
141 words
A color correction method for correcting colors in a color image, comprising: a standard point registration step for registering coordinates in a color space of at least one standard point, the color space having axes for specifying colors and a standard point representing a color to be used as a standard for color correction; an object point registration step for registering coordinates in the color space of an object point for each standard point, each object point representing a desired color to be achieved by color correction of a standard point; and a coordinate conversion step for determining a mapping function which maps each standard point to a corresponding object point and which can be used for mapping any arbitrary point in the color space, and for generating a corrected color image from an inputted pre-correction image using the mapping function.
Claim 19
Dependent Claim
53 words
The color correction method of Claim 18, wherein the mapping function is a function where an effect of a standard point on an amount which an arbitrary point in the pre-correction image is moved during mapping decreases as a distance in the color space from said pre-correction point to said standard point increases.
Claim 20
Dependent Claim
144 words
The color correction method of Claim 19, wherein the coordinate conversion step includes: a standard movement amount calculation step for calculating a standard movement amount for each standard point, said standard movement amount being a standard value used in determining an amount which a point in the pre-correction image is moved during mapping; a first weighting coefficient calculation step for calculating a weighting coefficient which corresponds to a distance from a standard point to a pre-correction point, using a fixed weighting coefficient function which has the weighting coefficient decrease uniformly with said distance; a summing step for summing products of a standard movement amount and the weighting coefficient, for every standard point; and a color image generation step for adding a value calculated by the summing step to the coordinates of the pre-correction point so as to generate a color in a corrected image.
Claim 21
Dependent Claim
164 words
The color correction method of Claim 20, wherein the standard movement amount calculation step includes: a correction amount calculation step for calculating a difference (hereinafter, correction amount) in the coordinates between a standard point and a corresponding object point, for every standard point; a distance calculation step for calculating a distance between all possible combinations of two standard points, including combinations where there is duplication of a same standard point; a second weighting coefficient calculation step for using the weighting coefficient function to calculate a weighting coefficient for each distance calculated by the distance calculation step; an inverse matrix generation step for generating an inverse matrix of a matrix, wherein weighting coefficients calculated by the second weighting coefficient calculation step are elements in said matrix; and a matrix multiplication step for multiplying the inverse matrix generated by the inverse matrix generation step by the correction amounts and for setting multiplication results as the standard movement amount, wherein there is a plurality of standard points.
Claim 22
Dependent Claim
38 words
The color correction method of Claim 18, wherein the mapping function is a function which performs interpolation and extrapolation for any arbitrary point in the color space setting all of the standard points and object points as standards.
Claim 23
Dependent Claim
63 words
The color correction method of Claim 22, wherein the coordinate conversion step includes: a distance determination step for comparing a distance on the color space between two standard points with a fixed threshold value; and a calculation order determination step for determining object points to be simultaneously used when executing interpolation and extrapolation, based on a comparison result for the distance determination step.
Claim 24
Dependent Claim
79 words
The color correction method of Claim 18, wherein the coordinate conversion step includes: an LUT storage step for storing a look up table (hereinafter, LUT) made up corresponding sets of coordinates for a plurality of predetermined points in the color space and coordinates of points achieved by mapping said points using the mapping function; and an LUT reference step for retrieving, once a pre-correction color image has been inputted, post-correction points corresponding to pre-correction points in the color image.
Claim 25
Dependent Claim
35 words
The color correction method of Claim 24, wherein the LUT reference step generates a corrected color image by retrieving a predetermined number of points in the LUT and executing an interpolation calculation between said points.
Claim 26
Dependent Claim
155 words
The color correction method of Claim 18, wherein the coordinate conversion step includes: a temporary storage step for storing coordinates obtained by conversion using the mapping function corresponded to points before conversion; a hit detection step for detecting, once a pre-correction color image is inputted, whether pre-correction points in the pre-correction color image are being stored by the temporary storage step; a temporary storage retrieval step for retrieving, when the hit detection step detects that the pre-correction points are being stored, converted points corresponding to the pre-conversion points from the temporary storage step, thereby generating the corrected color image; and temporary storage writing step for writing, when the hit detection step detects that the pre-correction points are not being stored, points which are converted according to the mapping function and corresponding pre-conversion points into the temporary storage step, as well as generating the points of the corrected color image from the points which are converted.
Claim 27
Dependent Claim
73 words
The color correction method of Claim 26, wherein the coordinate conversion step further includes: a temporary storage updating step for detecting whether there is free space for storing in the temporary storage step and, when a detection result is that there is no space for storing, for ensuring there is sufficient space for the temporary storage writing step to write by deleting a content at an appropriate position in the temporary storage step.
Claim 28
Dependent Claim
45 words
The color correction method of Claim 27, wherein the temporary storage step stores coordinates of post-conversion points at blocks corresponded to coordinates of pre-conversion points, and the hit detection step detects whether a pre-conversion point is stored by the temporary storage step using the blocks.
Claim 29
Dependent Claim
51 words
The color correction method of Claim 18, further including correction standard indication step for receiving an indication of any arbitrary point in the color space and for storing said point as the standard point in the standard point registration step and as the object point in the object point registration step.
Claim 30
Dependent Claim
83 words
The color correction method of Claim 29, wherein the correction standard indication step includes: a display step; an input operation step for receiving an indication from the user; and a display control step for displaying an operation image on the display step, for determining the standard point and the object point based on an indication received via the input operation step, and for storing the standard point in the standard point registration step and the object point in the object point registration step.
Claim 31
Dependent Claim
130 words
The color correction method of Claim 30, wherein the display control step includes: an image display step for displaying the pre-correction color image and the corrected color image on the display step; and a storage step for obtaining, when a pixel in the pre-correction color image is indicated by the input operation step, coordinates of said pixel as the standard point and an object point, for obtaining, when a pixel in the corrected color image is indicated by the input operation step, coordinates of said pixel as an object point, and coordinates of a pixel in a corresponding position in the pre-correction color image as the standard point, and for storing the standard point in the standard point registration step and the object point in the object point registration step.
Claim 32
Dependent Claim
42 words
The color correction method of Claim 30, wherein the display control step includes correction standard display step for displaying every pairing of standard point and object point indicated by the input indication step arranged into a same window on the display step.
Claim 33
Dependent Claim
64 words
The color correction method of Claim 32, wherein the display control step includes object point conversion step for setting, once a pairing of standard point and object point displayed in the same window have been selected by step of the input indication step, the object point in the pairing to be edited, and obtaining a newly indicated object point as a valid object point.
Claim 34
Dependent Claim
53 words
The color correction method of Claim 33, wherein the object point conversion step displays at least one of sliders, sample colors, and numerical values in order to correct values of the object point in each axis of the color space and receives an editing based on an indication by the input indication step.
References Cited (Backward Citations)
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