System for manipulating noise in digital images
First Claim
1. A method for analyzing noise content in a digital image, comprising:
- using a computer to perform;
sampling regions of the digital image;
discarding sampled regions that do not satisfy a pre-specified condition, wherein said discarding sampled regions that do not satisfy the pre-specified condition involves;
discarding sampled regions that are underexposed or overexposed;
computing the variance of the pixel values in each remaining sampled region; and
discarding sampled regions where the variance is above a pre-specified value;
extracting noise information from each remaining sampled region; and
generating a mathematical model of the noise using the noise information.
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Abstract
An apparatus for analyzing the broadband noise content of a digital image comprising the following: a means of automatically identifying regions of originally constant color in the image by analysis of the variance of pixel values of regions of the image; a means of automatically detecting and discarding regions deemed to be unrepresentative of the true noise content of an image, including under- and over- exposed regions; a means of allowing the user to manually select some or all required constant color regions if desired; and, a means of analyzing such constant color regions to generate a parametric or non-parametric model of the noise in the image, including frequency characteristic within and between channels and other characteristics such as phase which might describe structured noise.
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Citations
23 Claims
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1. A method for analyzing noise content in a digital image, comprising:
using a computer to perform; sampling regions of the digital image; discarding sampled regions that do not satisfy a pre-specified condition, wherein said discarding sampled regions that do not satisfy the pre-specified condition involves; discarding sampled regions that are underexposed or overexposed; computing the variance of the pixel values in each remaining sampled region; and discarding sampled regions where the variance is above a pre-specified value; extracting noise information from each remaining sampled region; and generating a mathematical model of the noise using the noise information. - View Dependent Claims (2, 3, 4, 7, 8, 9, 10, 11)
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5. A method for analyzing noise content in a digital image, comprising:
using a computer to perform; sampling regions of the digital image; discarding sampled regions that do not satisfy a pre-specified condition; extracting noise information from each remaining sampled region, wherein said extracting noise information from each remaining sampled region involves; for each remaining sampled region; computing the mean of the pixel values for the remaining sampled region to generate a mean pixel value; and subtracting the mean pixel value from the remaining sampled region, thereby generating sampled regions containing noise information, but no image content; and generating a mathematical model of the noise using the noise information.
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6. A method for analyzing noise content in a digital image, comprising:
using a computer to perform; sampling regions of the digital image; discarding sampled regions that do not satisfy a pre-specified condition; extracting noise information from each remaining sampled region; and generating a mathematical model of the noise using the noise information, wherein said generating a mathematical model of the noise using the noise information involves; applying a discrete Fourier transform to each remaining sampled region and to an auto correlation function of the noise; taking the square of the discrete Fourier transforms; averaging the squares of the discrete Fourier transforms; and selecting a best-fit linear-combination of the averages to generate the power spectral density of the noise for the digital image.
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12. A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for analyzing noise content in a digital image, the method comprising:
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sampling regions of the digital image; discarding sampled regions that do not satisfy a pre-specified condition, wherein said discarding sampled regions that do not satisfy the pre-specified condition involves; discarding sampled regions that are underexposed or overexposed; computing the variance of the pixel values in each remaining sampled region; and discarding sampled regions where the variance is above a pre-specified value; extracting noise information from each remaining sampled region; and generating a mathematical model of the noise using the noise information. - View Dependent Claims (13, 14, 15, 18, 19, 20, 21, 22)
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16. A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for analyzing noise content in a digital image, the method comprising:
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sampling regions of the digital image; discarding sampled regions that do not satisfy a pre-specified condition; extracting noise information from each remaining sampled region, wherein said extracting noise information from each remaining sampled region involves; for each remaining sampled region; computing the mean of the pixel values for the remaining sampled region to generate a mean pixel value; and subtracting the mean pixel value from the remaining sampled region, thereby generating sampled regions containing noise information, but no image content; and generating a mathematical model of the noise using the noise information.
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17. A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for analyzing noise content in a digital image, the method comprising:
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sampling regions of the digital image; discarding sampled regions that do not satisfy a pre-specified condition; extracting noise information from each remaining sampled region; and generating a mathematical model of the noise using the noise information, wherein said generating a mathematical model of the noise using the noise information involves; applying a discrete Fourier transform to each remaining sampled region and to an auto correlation function of the noise; taking the square of the discrete Fourier transforms; averaging the squares of the discrete Fourier transforms; and selecting a best-fit linear-combination of the averages to generate the power spectral density of the noise for the digital image.
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23. An apparatus for analyzing noise content in a digital image, comprising:
a noise analysis mechanism configured to; sample regions of the digital image; discard sampled regions that do not satisfy a pre-specified condition;
wherein to discard sampled regions that do not satisfy the pre-specified condition, the noise analysis mechanism is further configured to;discard sampled regions that are underexposed or overexposed; compute the variance of the pixel values in each remaining sampled region; and discard sampled regions where the variance is above a pre-specified value; extract noise information from each remaining sampled region; and generate a mathematical model of the noise using the noise information.
Specification