Noise reduction method, medium, and system
First Claim
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1. A noise reduction method, comprising:
- calculating a noise level of an input image;
decomposing the input image into pixels of different color channels;
determining an edge type of an edge of a central pixel;
controlling a removing of noise from the central pixel, within a window in the input image of a predetermined size including respective pixels of the different color channels, using a weight determined with respect to the edge type of the central pixel, based on a difference between signal intensities of the central pixel of a respective color channel and a plurality of adjacent pixels of the respective color channel within the window and the calculated noise level excluding pixels within the window of a color channel different from the respective color channel; and
determining whether impulse noise is contained in the central pixel, using plural threshold values,wherein when the impulse noise is determined to be contained in the central pixel, outputting a mean of weighted sums comprising outputting a mean of signal intensities of the plurality of adjacent pixels as a final signal intensity of the central pixel,wherein the outputting of the mean of the weighted sums comprises determining whether the impulse noise is contained in the central pixel using a rank-ordered absolute differences statistic (ROAD) calculated for the window.
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Abstract
A noise reduction method, medium, and system. The noise reduction method includes calculating a noise level of an input image and removing noise from a central pixel within a window of a predetermined size in the input image using a weight determined based on a difference between signal intensities of the central pixel and a plurality of adjacent pixels within the window and the calculated noise level.
14 Citations
33 Claims
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1. A noise reduction method, comprising:
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calculating a noise level of an input image; decomposing the input image into pixels of different color channels; determining an edge type of an edge of a central pixel; controlling a removing of noise from the central pixel, within a window in the input image of a predetermined size including respective pixels of the different color channels, using a weight determined with respect to the edge type of the central pixel, based on a difference between signal intensities of the central pixel of a respective color channel and a plurality of adjacent pixels of the respective color channel within the window and the calculated noise level excluding pixels within the window of a color channel different from the respective color channel; and determining whether impulse noise is contained in the central pixel, using plural threshold values, wherein when the impulse noise is determined to be contained in the central pixel, outputting a mean of weighted sums comprising outputting a mean of signal intensities of the plurality of adjacent pixels as a final signal intensity of the central pixel, wherein the outputting of the mean of the weighted sums comprises determining whether the impulse noise is contained in the central pixel using a rank-ordered absolute differences statistic (ROAD) calculated for the window. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 15, 16, 17)
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12. A noise reduction method, comprising:
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calculating a noise level of an input image; and controlling a removing of noise from a central pixel within a window of a predetermined size in the input image using a weight determined based on a difference between signal intensities of the central pixel and a plurality of adjacent pixels within the window and the calculated noise level, wherein the removal of the noise from the central pixel comprises; calculating weights to be assigned to the plurality of adjacent pixels based on differences between the signal intensities and the calculated noise level; compensating for the calculated weights according to an edge direction of the central pixel; and outputting a mean of weighted sums between the signal intensities of the central pixel and the plurality of adjacent pixels as a final signal intensity of the central pixel, wherein the outputting of the mean of the weighted sums comprises outputting a mean of signal intensities of the plurality of adjacent pixels as the final signal intensity of the central pixel when impulse noise is determined to be contained in the central pixel, wherein the outputting of the mean of the weighted sums comprises determining whether the impulse noise is contained in the central pixel using a rank-ordered absolute differences statistic (ROAD) calculated for the window, wherein the mean of the weighted sums is calculated using the calculated weights, and wherein the determination of whether the impulse noise is contained in the central pixel comprises determining that the impulse noise is not contained in the central pixel when the ROAD is less than a first threshold value but greater than a second threshold value and a variance of the signal intensities of the central pixel and the plurality of adjacent pixels is greater than a third threshold value.
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13. A noise reduction method, comprising:
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calculating a noise level of an input image; and controlling a removing of noise from a central pixel within a window of a predetermined size in the input image using a weight determined based on a difference between signal intensities of the central pixel and a plurality of adjacent pixels within the window and the calculated noise level, wherein the removal of the noise from the central pixel comprises; calculating weights to be assigned to the plurality of adjacent pixels based on differences between the signal intensities and the calculated noise level; compensating for the calculated weights according to an edge direction of the central pixel; and outputting a mean of weighted sums between the signal intensities of the central pixel and the plurality of adjacent pixels as a final signal intensity of the central pixel, wherein the outputting of the mean of the weighted sums comprises outputting a mean of signal intensities of the plurality of adjacent pixels as the final signal intensity of the central pixel when impulse noise is determined to be contained in the central pixel, wherein the outputting of the mean of the weighted sums comprises determining whether the impulse noise is contained in the central pixel using a rank-ordered absolute differences statistic (ROAD) calculated for the window, wherein the mean of the weighted sums is calculated using the calculated weights, and wherein the determination of whether the impulse noise is contained in the central pixel comprises determining that the impulse noise is contained in the central pixel if all differences between the signal intensities of the central pixel and the plurality of adjacent pixels are greater than a fourth threshold value when the ROAD is less than a first threshold value but greater than the second threshold value and the variance of the signal intensities of the central pixel and the plurality of adjacent pixels is less than the third threshold value. - View Dependent Claims (14)
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18. A system with noise reduction, comprising:
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a noise level calculation unit to calculate a noise level of an input image; an edge determination unit to determine an edge type of an edge of a central pixel; a filtering unit to decompose the input image into pixels of different color channels, control a removing of noise from the central pixel, within a window in the input image of a predetermined size including respective pixels of the different color channels, using a weight determined, with respect to the edge type of the central pixel, based on a difference between signal intensities of the central pixel of a respective color channel and plurality of adjacent pixels of the respective color channel within the window and the calculated noise level excluding pixels within the window of a color channel different from the respective color channel; and an impulse noise determination unit to determine whether impulse noise is contained in the central pixel, using plural threshold values, wherein when the impulse noise is determined to be contained in the central pixel, outputting a mean of weighted sums comprising outputting a mean of signal intensities of the plurality of adjacent pixels as a final signal intensity of the central pixel, wherein the outputting of the mean of the weighted sums comprises determining whether the impulse noise is contained in the central pixel using a rank-ordered absolute differences statistic (ROAD) calculated for the window. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 32)
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29. A system with noise reduction, comprising:
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a noise level calculation unit to calculate a noise level of an input image; a filtering unit to control a removing of noise from a central pixel within a window of a predetermined size in the input image using a weight determined based on a difference between signal intensities of the central pixel and plurality of adjacent pixels within the window and the calculated noise level; a weight calculation unit to calculate weights to be assigned to the plurality of adjacent pixels based on differences between the signal intensities and the calculated noise level; a weight compensation unit to compensate for the calculated weights according to an edge direction of the central pixel; and an impulse noise determination unit which determines whether impulse noise is contained in the central pixel using a ROAD calculated for the window, wherein the filtering unit calculates and outputs a mean of weighted sums of the signal intensities of the central pixel and the plurality of adjacent pixels using the calculated weights as a final signal intensity of the central pixel when the impulse noise is determined to not be contained in the central pixel, and outputs a mean of signal intensities of the plurality of adjacent pixels as the final signal intensity of the central pixel when the impulse noise is determined to be contained in the central pixel, wherein the impulse noise determination unit determines that the impulse noise is not contained in the central pixel when the ROAD is less than the first threshold value but greater than a second threshold value and a variance of the signal intensities of the central pixel and the plurality of adjacent pixels is greater than a third threshold value.
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30. A system with noise reduction, comprising:
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a noise level calculation unit to calculate a noise level of an input image; a filtering unit to control a removing of noise from a central pixel within a window of a predetermined size in the input image using a weight determined based on a difference between signal intensities of the central pixel and plurality of adjacent pixels within the window and the calculated noise level; a weight calculation unit to calculate weights to be assigned to the plurality of adjacent pixels based on differences between the signal intensities and the calculated noise level; a weight compensation unit to compensate for the calculated weights according to an edge direction of the central pixel; and an impulse noise determination unit which determines whether impulse noise is contained in the central pixel using a ROAD calculated for the window, wherein the filtering unit calculates and outputs a mean of weighted sums of the signal intensities of the central pixel and the plurality of adjacent pixels using the calculated weights, with the output mean being a final signal intensity of the central pixel, wherein the filtering unit outputs a mean of signal intensities of the plurality of adjacent pixels as the final signal intensity of the central pixel when the impulse noise is determined to be contained in the central pixel, wherein the impulse noise determination unit determines that the impulse noise is contained in the central pixel if all differences between the signal intensities of the central pixel and the plurality of adjacent pixels are greater than a fourth threshold value when the ROAD is less than the first threshold value but greater than the second threshold value and the variance of the signal intensities of the central pixel and the plurality of adjacent pixels is less than the third threshold value. - View Dependent Claims (31)
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33. A photographing system, comprising:
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a photographing unit to photograph a subject as an input image; an edge determination unit to determine an edge type of an edge of a central pixel; a noise reduction unit to decompose the input image into pixels of different color channels, calculate a noise level of the input image and control a removal of noise from the central pixel, within a window in the input image of a predetermined size including respective pixels of the different color channels, using a weight determined with respect to the edge type of the central pixel, based on a difference between signal intensities of the central pixel of a respective color channel and a plurality of adjacent pixels of the respective color channel within the window and the calculated noise level excluding pixels within the window of a color channel different from the respective color channel; and an impulse noise determination unit to determine whether impulse noise is contained in the central pixel, using plural threshold values, wherein when the impulse noise is determined to be contained in the central pixel, outputting a mean of weighted sums comprising outputting a mean of signal intensities of the plurality of adjacent pixels as a final signal intensity of the central pixel, wherein the outputting of the mean of the weighted sums comprises determining whether the impulse noise is contained in the central pixel using a rank-ordered absolute differences statistic (ROAD) calculated for the window.
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Specification