US7881554B2
Expired / Lapsed
US
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Method for correcting a digital image
Assignee: STMicroelectronics SRL
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Filing: 2006-06-05
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Granted: 2011-02-01
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Expires: 2026-06-05
Abstract
Abstract A luminance intensity of pixels of an input digital image is corrected for generating a corrected digital image. A luminance of each pixel is calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function. A mask of the input digital image to be corrected is generated according to a bilateral filtering technique. For each pixel of the input digital image, a respective value of at least one parameter of the parametric function is established based upon the luminance of a corresponding pixel of the mask.
Inventors
- 👤 Alfio Castorina
- 👤 Raimondo Schettini
- 👤 Francesca Gasparini
- 👤 Silvia Corchs
- 👤 Alessandro Capra
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 16:46
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/90; G06T5/94; G06T5/20; G06T2207/00; G06T2207/10; G06T2207/10024; G06T2207/20; G06T2207/20024; G06T2207/20028; G06T2207/20172; G06T2207/20192
Claims Analysis
Total Claims: 42
Claim 1
Independent Claim
275 words
A method for correcting a luminance intensity of pixels of an input digital image for generating a corrected digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the method comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask; establishing a number of dark pixels in the corrected digital image and in the input digital image; if there are dark pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of dark pixels as in the input digital image, then performing a clipping operation based upon a first percentage; if there are no dark pixels in the input digital image, performing the stretching operation and the clipping operation to clip a second percentage of the darkest pixels; establishing a number of bright pixels in the corrected digital image and in the input digital image; if there are bright pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of bright pixels as in the input digital image, then performing a clipping operation based upon the second percentage; and if there are no bright pixels in the input digital image, performing the stretching operation and the clipping operation to clip the second percentage of the brightest pixels.
Claim 2
Independent Claim
275 words
A method for correcting a luminance intensity of pixels of an input digital image for generating a corrected digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the method comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask; establishing a number of dark pixels in the corrected digital image and in the input digital image; if there are dark pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of dark pixels as in the input digital image, then performing a clipping operation based upon a first percentage; if there are no dark pixels in the input digital image, performing the stretching operation and the clipping operation to clip a second percentage of the darkest pixels; establishing a number of bright pixels in the corrected digital image and in the input digital image; if there are bright pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of bright pixels as in the input digital image, then performing a clipping operation based upon the second percentage; and if there are no bright pixels in the input digital image, performing the stretching operation and the clipping operation to clip the second percentage of the brightest pixels.
Claim 3
Dependent Claim
30 words
A method according to claim 1 , wherein the parametric function is a power operator of a gamma correction operation, an exponent of which is the at least one parameter.
Claim 4
Dependent Claim
50 words
A method according to claim 2 , wherein the exponent is obtained by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity.
Claim 5
Dependent Claim
27 words
A method according to claim 3 , further comprising determining the real number as a function of a threshold mean luminance intensity of the corrected digital image.
Claim 6
Dependent Claim
114 words
A method according to claim 4 , wherein for the original image, the threshold mean luminance is smaller than the median luminance intensity, and the real number is a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; and if the mean luminance of the input digital image is larger than the median luminance intensity, then the real number is the ratio between the natural logarithm of 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 7
Dependent Claim
28 words
A method according to claim 4 , further comprising checking whether the real number is within a range, and if so, then leaving uncorrected the input digital image.
Claim 8
Dependent Claim
15 words
A method according to claim 6 , wherein the range is from 1 to 1.2.
Claim 9
Dependent Claim
68 words
A method according to claim 1 , wherein generating the mask comprises: generating an inverted black and white replica of the input digital image to be corrected, wherein the luminance intensity of each pixel is the difference between a threshold luminance intensity and the luminance intensity of the corresponding input digital image; and low-pass bilateral filtering of the inverted black and white replica of the input digital image.
Claim 10
Dependent Claim
27 words
A method according to claim 1 , further comprising shrinking the input digital image with a scale factor to analyze and estimate a strength of the correction.
Claim 11
Dependent Claim
19 words
A method according to claim 1 , wherein the first percentage is 30% and the second percentage is 0.2%.
Claim 12
Dependent Claim
131 words
A method according to claim 1 , wherein the input digital image is an RGB digital image; and further comprising: correcting the color saturation of the corresponding corrected digital image according to the following formula: { R ′ = 1 2 ( Y ′ Y ( R + Y ) + R - Y ) G ′ = 1 2 ( Y ′ Y ( G + Y ) + G - Y ) B ′ = 1 2 ( Y ′ Y ( B + Y ) + B - Y ) wherein R, G, B, Y are the red, green blue and luminance components of the corrected digital image, respectively, and R′, G′, B′ Y′ are the corresponding components of the final image.
Claim 13
Independent Claim
353 words
A method for correcting a luminance intensity of pixels of an input digital image for generating a corrected digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the method comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique by at least generating an inverted black and white replica of the input digital image to be corrected, wherein the luminance intensity of each pixel is a difference between a threshold luminance intensity and the luminance intensity of the corresponding input digital image, and filtering the inverted black and white replica of the input digital image; for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; establishing a number of dark pixels in the corrected digital image and in the input digital image; if there are dark pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of dark pixels as in the input digital image, then performing a clipping operation based upon a first percentage; if there are no dark pixels in the input digital image, performing the stretching operation and the clipping operation to clip a second percentage of the darkest pixels; establishing a number of bright pixels in the corrected digital image and in the input digital image; if there are bright pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of bright pixels as in the input digital image, then performing a clipping operation based upon the second percentage; and if there are no bright pixels in the input digital image, performing the stretching operation and the clipping operation to clip the second percentage of the brightest pixels.
Claim 14
Independent Claim
353 words
A method for correcting a luminance intensity of pixels of an input digital image for generating a corrected digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the method comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique by at least generating an inverted black and white replica of the input digital image to be corrected, wherein the luminance intensity of each pixel is a difference between a threshold luminance intensity and the luminance intensity of the corresponding input digital image, and filtering the inverted black and white replica of the input digital image; for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; establishing a number of dark pixels in the corrected digital image and in the input digital image; if there are dark pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of dark pixels as in the input digital image, then performing a clipping operation based upon a first percentage; if there are no dark pixels in the input digital image, performing the stretching operation and the clipping operation to clip a second percentage of the darkest pixels; establishing a number of bright pixels in the corrected digital image and in the input digital image; if there are bright pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of bright pixels as in the input digital image, then performing a clipping operation based upon the second percentage; and if there are no bright pixels in the input digital image, performing the stretching operation and the clipping operation to clip the second percentage of the brightest pixels.
Claim 15
Dependent Claim
18 words
A method according to claim 12 , wherein the threshold luminance intensity corresponds to a maximum luminance intensity.
Claim 16
Dependent Claim
50 words
A method according to claim 12 , wherein the exponent is obtained by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity.
Claim 17
Dependent Claim
27 words
A method according to claim 14 , further comprising determining the real number as a function of a threshold mean luminance intensity of the corrected digital image.
Claim 18
Dependent Claim
114 words
A method according to claim 15 , wherein for the original image, the threshold mean luminance is smaller than the median luminance intensity, and the real number is a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; and if the mean luminance of the input digital image is larger than the median luminance intensity, then the real number is the ratio between the natural logarithm of 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 19
Dependent Claim
28 words
A method according to claim 15 , further comprising checking whether the real number is within a range, and if so, then leaving uncorrected the input digital image.
Claim 20
Dependent Claim
19 words
A method according to claim 12 , wherein the first percentage is 30% and the second percentage is 0.2%.
Claim 21
Dependent Claim
286 words
A computer-readable medium having computer-executable instructions for causing a computer to correct a luminance intensity of pixels of an input digital image by generating a corrected digital image, the luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the computer to perform steps comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask; establishing a number of dark pixels in the corrected digital image and in the input digital image; if there are dark pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of dark pixels as in the input digital image, then performing a clipping operation based upon a first percentage; if there are no dark pixels in the input digital image, performing the stretching operation and the clipping operation to clip a second percentage of the darkest pixels; establishing a number of bright pixels in the corrected digital image and in the input digital image; if there are bright pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of bright pixels as in the input digital image, then performing a clipping operation based upon the second percentage; and if there are no bright pixels in the input digital image, performing the stretching operation and the clipping operation to clip the second percentage of the brightest pixels.
Claim 22
Dependent Claim
286 words
A computer-readable medium having computer-executable instructions for causing a computer to correct a luminance intensity of pixels of an input digital image by generating a corrected digital image, the luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the computer to perform steps comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask; establishing a number of dark pixels in the corrected digital image and in the input digital image; if there are dark pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of dark pixels as in the input digital image, then performing a clipping operation based upon a first percentage; if there are no dark pixels in the input digital image, performing the stretching operation and the clipping operation to clip a second percentage of the darkest pixels; establishing a number of bright pixels in the corrected digital image and in the input digital image; if there are bright pixels in the input digital image, performing a stretching operation on the corrected digital image to have a same percentage of bright pixels as in the input digital image, then performing a clipping operation based upon the second percentage; and if there are no bright pixels in the input digital image, performing the stretching operation and the clipping operation to clip the second percentage of the brightest pixels.
Claim 23
Dependent Claim
31 words
A computer-readable medium according to claim 19 , wherein the parametric function is a power operator of a gamma correction operation, an exponent of which is the at least one parameter.
Claim 24
Dependent Claim
51 words
A computer-readable medium according to claim 20 , wherein the exponent is obtained by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity.
Claim 25
Dependent Claim
28 words
A computer-readable medium according to claim 21 , further comprising determining the real number as a function of a threshold mean luminance intensity of the corrected digital image.
Claim 26
Dependent Claim
115 words
A computer-readable medium according to claim 22 , wherein for the original image, the threshold mean luminance is smaller than the median luminance intensity, and the real number is a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; and if the mean luminance of the input digital image is larger than the median luminance intensity, then the real number is the ratio between the natural logarithm of 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 27
Dependent Claim
29 words
A computer-readable medium according to claim 22 , further comprising checking whether the real number is within a range, and if so, then leaving uncorrected the input digital image.
Claim 28
Dependent Claim
16 words
A computer-readable medium according to claim 24 , wherein the range is from 1 to 1.2.
Claim 29
Dependent Claim
69 words
A computer-readable medium according to claim 19 , wherein generating the mask comprises: generating an inverted black and white replica of the input digital image to be corrected, wherein the luminance intensity of each pixel is the difference between a threshold luminance intensity and the luminance intensity of the corresponding input digital image; and low-pass bilateral filtering of the inverted black and white replica of the input digital image.
Claim 30
Dependent Claim
28 words
A computer-readable medium according to claim 19 , further comprising shrinking the input digital image with a scale factor to analyze and estimate a strength of the correction.
Claim 31
Dependent Claim
20 words
A computer-readable medium according to claim 19 , wherein the first percentage is 30% and the second percentage is 0.2%.
Claim 32
Dependent Claim
132 words
A computer-readable medium according to claim 19 , wherein the input digital image is an RGB digital image; and further comprising: correcting the color saturation of the corresponding corrected digital image according to the following formula: { R ′ = 1 2 ( Y ′ Y ( R + Y ) + R - Y ) G ′ = 1 2 ( Y ′ Y ( G + Y ) + G - Y ) B ′ = 1 2 ( Y ′ Y ( B + Y ) + B - Y ) wherein R, C, B, Y are the red, green blue and luminance components of the corrected digital image, respectively, and R′, G′, B′ Y′ are the corresponding components of the final image.
Claim 33
Independent Claim
316 words
An apparatus comprising: an input configured to receive an input digital image; and a processor configured to correct a luminance intensity of pixels of the input digital image for generating a corrected digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the correcting comprising generating a mask of the input digital image to be corrected according to a bilateral filtering technique, for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of a gamma correction operation, an exponent of which being the at least one parameter; obtaining the exponent by powering a real number to an exponent given by a ratio between a difference to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; and determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; for the original image, the threshold mean luminance being smaller than the median luminance intensity, and the real number being a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; if the mean luminance of the input digital image is larger than the median luminance intensity, then the real number is the ratio between the natural logarithm of 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 34
Independent Claim
316 words
An apparatus comprising: an input configured to receive an input digital image; and a processor configured to correct a luminance intensity of pixels of the input digital image for generating a corrected digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the correcting comprising generating a mask of the input digital image to be corrected according to a bilateral filtering technique, for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of a gamma correction operation, an exponent of which being the at least one parameter; obtaining the exponent by powering a real number to an exponent given by a ratio between a difference to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; and determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; for the original image, the threshold mean luminance being smaller than the median luminance intensity, and the real number being a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; if the mean luminance of the input digital image is larger than the median luminance intensity, then the real number is the ratio between the natural logarithm of 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 35
Independent Claim
284 words
A method for correcting a luminance intensity of pixels of an input digital image for generating a corrected digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to parametric function, the method comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; obtaining the exponent by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; and determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; in the original image, the threshold mean luminance being smaller than the median luminance intensity, and the real number being a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; if the mean luminance of the input digital image is larger than the median luminance intensity, then the real number is the ratio between the natural logarithm of 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 36
Independent Claim
284 words
A method for correcting a luminance intensity of pixels of an input digital image for generating a corrected digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to parametric function, the method comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; obtaining the exponent by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; and determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; in the original image, the threshold mean luminance being smaller than the median luminance intensity, and the real number being a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; if the mean luminance of the input digital image is larger than the median luminance intensity, then the real number is the ratio between the natural logarithm of 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 37
Independent Claim
210 words
A method for correcting a luminance intensity of pixels of an input digital image for generating a corrected a digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the method comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; and for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; obtaining the exponent by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; and checking whether the real number is within a range between a value of greater than 1 and 1.2, and if so, then leaving uncorrected the input digital image.
Claim 38
Independent Claim
210 words
A method for correcting a luminance intensity of pixels of an input digital image for generating a corrected a digital image, a luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the method comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; and for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; obtaining the exponent by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; and checking whether the real number is within a range between a value of greater than 1 and 1.2, and if so, then leaving uncorrected the input digital image.
Claim 39
Dependent Claim
298 words
A computer-readable medium having computer-executable instructions for causing a computer to correct a luminance intensity of pixels of an input digital image by generating a corrected digital image, the luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the computer to perform steps comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; and for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; obtaining the exponent by powering a real number to an exponent give by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; and determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; for the original image, the threshold mean luminance being smaller than the median luminance intensity, and the real number being a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; if the mean luminance of the input digital image is larger than the median luminance intensity, them the real number is the ratio between the natural logarithm of the 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 40
Dependent Claim
298 words
A computer-readable medium having computer-executable instructions for causing a computer to correct a luminance intensity of pixels of an input digital image by generating a corrected digital image, the luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the computer to perform steps comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; and for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; obtaining the exponent by powering a real number to an exponent give by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; and determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; for the original image, the threshold mean luminance being smaller than the median luminance intensity, and the real number being a ratio between a natural logarithm of the mean luminance intensity of the input digital image to be corrected and a natural logarithm of the median luminance intensity; if the mean luminance of the input digital image is larger than the median luminance intensity, them the real number is the ratio between the natural logarithm of the 2 n−1 and the natural logarithm of the mean luminance intensity of the input digital image to be corrected, n representing a bit depth of the input digital image.
Claim 41
Dependent Claim
220 words
A computer-readable medium having computer-executable instructions for causing a computer to correct a luminance intensity of pixel of an input digital image by generating a corrected digital image, the luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the computer to perform steps comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; and for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; obtaining the exponent by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; and checking whether the real number is within a range between a value of greater than 1 and 1.2, and if so, then leaving uncorrected the input digital image.
Claim 42
Dependent Claim
220 words
A computer-readable medium having computer-executable instructions for causing a computer to correct a luminance intensity of pixel of an input digital image by generating a corrected digital image, the luminance of each pixel being calculated as a function of the luminance of a corresponding pixel in an original image according to a parametric function, the computer to perform steps comprising: generating a mask of the input digital image to be corrected according to a bilateral filtering technique; and for each pixel of the input digital image, establishing a respective value of at least one parameter of the parametric function based upon the luminance of a corresponding pixel of the mask, the parametric function being a power operator of a gamma correction operation, an exponent of which is the at least one parameter; obtaining the exponent by powering a real number to an exponent given by a ratio between a difference between a median luminance intensity and a value of the mask corresponding to the pixel to be corrected, and the median luminance intensity; determining the real number as a function of a threshold mean luminance intensity of the corrected digital image; and checking whether the real number is within a range between a value of greater than 1 and 1.2, and if so, then leaving uncorrected the input digital image.
References Cited (Backward Citations)
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Cited
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