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US6038339A
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White point determination using correlation matrix memory
Assignee: HP Inc
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Filing: 1997-11-14
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Granted: 2000-03-14
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Expires: 2017-11-14
Abstract
Abstract Color digital imaging quality is improved by quickly, accurately and robustly estimating illuminant information associated with a color digital image to correct color of the image based on the illuminant. A "correlation matrix memory" or "associative matrix memory" is used to achieve identical results to the Color in Perspective method, and to improve it by adding Bayesian or other correlation statistics. The new method is insensitive to aperture colors and provides an effective framework on top of estimation. It will effortlessly return the maximum likelihood answer. A correlation matrix memory is built to correlate the data from any picture image to reference images under a range of illuminants. When a camera, scanner, or the like, produces a picture image, the data is converted to chromaticity and a vector is created corresponding to the values existing in the scene. This vector is multiplied by each column in the correlation matrix giving a new matrix. Each column is then summed, and the resulting values form a vector that represents the likelihood of each reference source being the illuminant of the scene. The vector values can be density plotted where each value is plotted at the chromaticity of the illumination for that particular column. From this plot normal statistical methods can be used to estimate the likely illumination of the scene. Greatly reduced computational requirements result because simple binary matrix algorithms replace complex geometrical calculations
Inventors
- 👤 Paul M. Hubel
- 👤 Graham Finlayson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 14:14
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/60; H04N1/6083; H04N1/6086; G; G06; G06T; G06T7/00; G06T7/90; G06T2207/00; G06T2207/10; G06T2207/10024
Claims Analysis
Total Claims: 50
Claim 1
Independent Claim
100 words
A process for a captured image, the captured image being a color digital image having an associated illuminant of unknown color, the process comprising the steps of: forming an image vector based on chromaticities associated with the captured image; applying the image vector to a correlation matrix to form a resulting vector, the correlation matrix having a first dimension corresponding to a set of candidate illuminants and having a second dimension corresponding to chromaticities; and based on the resulting vector, selecting at least one candidate illuminant from the set of candidate illuminants to be the associated illuminant of unknown color.
Claim 2
Dependent Claim
100 words
A process for a captured image, the captured image being a color digital image having an associated illuminant of unknown color, the process comprising the steps of: forming an image vector based on chromaticities associated with the captured image; applying the image vector to a correlation matrix to form a resulting vector, the correlation matrix having a first dimension corresponding to a set of candidate illuminants and having a second dimension corresponding to chromaticities; and based on the resulting vector, selecting at least one candidate illuminant from the set of candidate illuminants to be the associated illuminant of unknown color.
Claim 3
Dependent Claim
97 words
The process as set forth in 1, wherein the image vector has positions, each of the positions corresponding to a particular chromaticity and wherein the step of forming an image vector includes the substeps of: converting RGB data from the captured image to chromaticities; setting a particular position of the image vector to a first value if the chromaticity corresponding to the particular position appears in the captured image; and setting the particular position of the image vector to a second value if the chromaticity corresponding to the particular position does not appear in the captured image.
Claim 4
Dependent Claim
97 words
The process as set forth in 1, wherein the image vector has positions, each of the positions corresponding to a particular chromaticity and wherein the step of forming an image vector includes the substeps of: converting RGB data from the captured image to chromaticities; setting a particular position of the image vector to a first value if the chromaticity corresponding to the particular position appears in the captured image; and setting the particular position of the image vector to a second value if the chromaticity corresponding to the particular position does not appear in the captured image.
Claim 5
Dependent Claim
19 words
The process as set forth in 2, wherein the first value is one and the second value is zero.
Claim 6
Dependent Claim
19 words
The process as set forth in 2, wherein the first value is one and the second value is zero.
Claim 7
Dependent Claim
30 words
The process as set forth in 1, wherein the step of applying the image vector to the correlation matrix involves matrix multiplication of the image vector and the correlation matrix.
Claim 8
Dependent Claim
30 words
The process as set forth in 1, wherein the step of applying the image vector to the correlation matrix involves matrix multiplication of the image vector and the correlation matrix.
Claim 9
Dependent Claim
38 words
The process as set forth in 1, wherein the step of applying the image vector to the correlation matrix involves matrix multiplication of the image vector and the correlation matrix to form a sum-vector as the resulting vector.
Claim 10
Dependent Claim
38 words
The process as set forth in 1, wherein the step of applying the image vector to the correlation matrix involves matrix multiplication of the image vector and the correlation matrix to form a sum-vector as the resulting vector.
Claim 11
Dependent Claim
25 words
The process as set forth in claim 5, wherein the step of selecting at least one candidate vector involves applying a threshold to the sum-vector.
Claim 12
Dependent Claim
22 words
The process as set forth in claim 5, wherein the sum-vector represents likelihoods of each the candidate illuminants being the unknown illuminant.
Claim 13
Dependent Claim
119 words
The process as set forth in claim 1, wherein for a particular candidate illuminant chromaticity, coordinates of the correlation matrix are obtained by the steps of: illuminating a set of reference surfaces with the particular candidate illuminant and computing chromaticities for the reference surfaces; finding a convex hull of the chromaticities for the reference surfaces to form a reference gamut for the particular candidate illuminant; and for each chromaticity of the second dimension, setting the chromaticity coordinate for the particular candidate illuminant to a first value if the chromaticity is present in the reference gamut, and setting the chromaticity coordinate for the particular candidate illuminant to a second value if the chromaticity is not present in the reference gamut.
Claim 14
Dependent Claim
19 words
The process as set forth in 8, wherein the first value is one and the second value is zero.
Claim 15
Dependent Claim
19 words
The process as set forth in 8, wherein the first value is one and the second value is zero.
Claim 16
Dependent Claim
15 words
The process as set forth in 1, comprising the step of capturing the captured image.
Claim 17
Dependent Claim
15 words
The process as set forth in 1, comprising the step of capturing the captured image.
Claim 18
Dependent Claim
38 words
The process as set forth in 1, comprising the step of using the associated illuminant obtained from the step of selecting at least one candidate illuminant to process the captured image and thereby form a color corrected image.
Claim 19
Dependent Claim
38 words
The process as set forth in 1, comprising the step of using the associated illuminant obtained from the step of selecting at least one candidate illuminant to process the captured image and thereby form a color corrected image.
Claim 20
Dependent Claim
16 words
The process as set forth in 11, comprising the step of outputting the color corrected image.
Claim 21
Dependent Claim
16 words
The process as set forth in 11, comprising the step of outputting the color corrected image.
Claim 22
Dependent Claim
36 words
The process as set forth in 1, comprising the step of using the associated illuminant obtained from the step of selecting at least one candidate illuminant to detect whether the unknown illuminant is a flash device.
Claim 23
Dependent Claim
36 words
The process as set forth in 1, comprising the step of using the associated illuminant obtained from the step of selecting at least one candidate illuminant to detect whether the unknown illuminant is a flash device.
Claim 24
Dependent Claim
26 words
The process as set forth in 13, comprising the step of adjusting the captured image to compensate for flash effects if the flash device was detected.
Claim 25
Dependent Claim
26 words
The process as set forth in 13, comprising the step of adjusting the captured image to compensate for flash effects if the flash device was detected.
Claim 26
Dependent Claim
103 words
A processor for a captured image, the captured image being a color digital image having an associated illuminant of unknown color, the processor comprising: means for forming an image vector based on chromaticities associated with the captured image; means for applying the image vector to a correlation matrix to form a resulting vector, the correlation matrix having a first dimension corresponding to a set of candidate illuminants and having a second dimension corresponding to chromaticities; and means for selecting, based on the resulting vector, at least one candidate illuminant from the set of candidate illuminants to be the associated illuminant of unknown color.
Claim 27
Dependent Claim
103 words
A processor for a captured image, the captured image being a color digital image having an associated illuminant of unknown color, the processor comprising: means for forming an image vector based on chromaticities associated with the captured image; means for applying the image vector to a correlation matrix to form a resulting vector, the correlation matrix having a first dimension corresponding to a set of candidate illuminants and having a second dimension corresponding to chromaticities; and means for selecting, based on the resulting vector, at least one candidate illuminant from the set of candidate illuminants to be the associated illuminant of unknown color.
Claim 28
Dependent Claim
99 words
The process as set forth in 15, wherein the image vector has positions, each of the positions corresponding to a particular chromaticity and wherein the means for forming an image vector includes: means for converting RGB data from the captured image to chromaticities; means for setting a particular position of the image vector to a first value if the chromaticity corresponding to the particular position appears in the captured image; and for setting the particular position of the image vector to a second value if the chromaticity corresponding to the particular position does not appear in the captured image.
Claim 29
Dependent Claim
99 words
The process as set forth in 15, wherein the image vector has positions, each of the positions corresponding to a particular chromaticity and wherein the means for forming an image vector includes: means for converting RGB data from the captured image to chromaticities; means for setting a particular position of the image vector to a first value if the chromaticity corresponding to the particular position appears in the captured image; and for setting the particular position of the image vector to a second value if the chromaticity corresponding to the particular position does not appear in the captured image.
Claim 30
Dependent Claim
19 words
The processor as set forth in 16, wherein the first value is one and the second value is zero.
Claim 31
Dependent Claim
19 words
The processor as set forth in 16, wherein the first value is one and the second value is zero.
Claim 32
Dependent Claim
27 words
The processor as set forth in 15, wherein applying the image vector to the correlation matrix involves matrix multiplication of the image vector and the correlation matrix.
Claim 33
Dependent Claim
27 words
The processor as set forth in 15, wherein applying the image vector to the correlation matrix involves matrix multiplication of the image vector and the correlation matrix.
Claim 34
Dependent Claim
35 words
The processor as set forth in 18 wherein applying the image vector to the correlation matrix involves matrix multiplication of the image vector and the correlation matrix to form a sum-vector as the resulting vector.
Claim 35
Dependent Claim
35 words
The processor as set forth in 18 wherein applying the image vector to the correlation matrix involves matrix multiplication of the image vector and the correlation matrix to form a sum-vector as the resulting vector.
Claim 36
Dependent Claim
22 words
The processor as set forth in claim 19, wherein selecting at least one candidate vector involves applying a threshold to the sum-vector.
Claim 37
Dependent Claim
22 words
The processor as set forth in claim 19, wherein the sum-vector represents likelihoods of each the candidate illuminants being the unknown illuminant.
Claim 38
Dependent Claim
119 words
The processor as set forth in claim 15, wherein for a particular candidate illuminant chromaticity, coordinates of the correlation matrix are obtained by the steps of: illuminating a set of reference surfaces with the particular candidate illuminant and computing chromaticities for the reference surfaces; finding a convex hull of the chromaticities for the reference surfaces to form a reference gamut for the particular candidate illuminant; and for each chromaticity of the second dimension, setting the chromaticity coordinate for the particular candidate illuminant to a first value if the chromaticity is present in the reference gamut, and setting the chromaticity coordinate for the particular candidate illuminant to a second value if the chromaticity is not present in the reference gamut.
Claim 39
Dependent Claim
19 words
The processor as set forth in 22, wherein the first value is one and the second value is zero.
Claim 40
Dependent Claim
19 words
The processor as set forth in 22, wherein the first value is one and the second value is zero.
Claim 41
Dependent Claim
14 words
The processor as set forth in 15, comprising means for capturing the captured image.
Claim 42
Dependent Claim
14 words
The processor as set forth in 15, comprising means for capturing the captured image.
Claim 43
Dependent Claim
38 words
The processor as set forth in 15, comprising color correction means for processing the captured image and thereby forming a color corrected image using the associated illuminant obtained from the means for selecting at least one candidate illuminant.
Claim 44
Dependent Claim
38 words
The processor as set forth in 15, comprising color correction means for processing the captured image and thereby forming a color corrected image using the associated illuminant obtained from the means for selecting at least one candidate illuminant.
Claim 45
Dependent Claim
15 words
The processor as set forth in 25, comprising means for outputting the color corrected image.
Claim 46
Dependent Claim
15 words
The processor as set forth in 25, comprising means for outputting the color corrected image.
Claim 47
Dependent Claim
37 words
The processor as set forth in 15, comprising a flash detector that uses the associated illuminant obtained from the step of selecting at least one candidate illuminant to detect whether the unknown illuminant is a flash device.
Claim 48
Dependent Claim
37 words
The processor as set forth in 15, comprising a flash detector that uses the associated illuminant obtained from the step of selecting at least one candidate illuminant to detect whether the unknown illuminant is a flash device.
Claim 49
Dependent Claim
27 words
The processor as set forth in 27, comprising a flash compensator to adjust the captured image to compensate for flash effects if the flash device was detected.
Claim 50
Dependent Claim
27 words
The processor as set forth in 27, comprising a flash compensator to adjust the captured image to compensate for flash effects if the flash device was detected.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2003-03-14 | 2003-09-13 | 2004-03-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-03-14 | 2007-09-13 | 2008-03-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-03-14 | 2011-09-13 | 2012-03-14 | $7700.00 | Window Closed / Lapsed |