Denoising method, apparatus, and program
First Claim
1. A denoising method comprising the steps of:
- generating, based on a digital image acquired by imaging a subject, a plurality of band-limited images respectively representing components of a plurality of frequency bands of said digital image;
obtaining a plurality of converted images by performing on respective pixel values of said band-limited images a nonlinear conversion process, in which an absolute value of an output value is reduced to an absolute value of an input value or less, and in which, for an input value whose absolute value is a predetermined threshold value or less, an absolute value of an output value becomes greater as an absolute value of said input value becomes greater and, for an input value whose absolute value is greater than said predetermined value, an absolute value of an output value becomes less than or equal to an absolute value of an output value corresponding to said predetermined threshold value;
multiplying the pixel values of said converted images by a predetermined subtraction coefficient; and
obtaining a pixel value of a processed image by subtracting the pixel values of said converted images multiplied by said predetermined subtraction coefficient, from a pixel value of said digital image.
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Accused Products
Abstract
A blurred image generating section generates a plurality of blurred images Sm (where m=1 to n and n≧2) different in frequency response characteristic from one another, based on an original image S0. A band-limited image generating section generates a plurality of band-limited images Tm by performing a subtraction between images of adjacent frequency bands, employing the original image S0 and each of the blurred images Sm. A noise component extraction section extracts converted images, obtained by performing nonlinear conversion on each of the band-limited images Tm, as noise components Qm contained in the different frequency bands. A noise-component elimination section subtracts from the original image S0 a value obtained by multiplying a subtraction coefficient β (which is determined according to the pixel value Y0 of the original image S0) and the sum of the noise components Qm together.
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Citations
11 Claims
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1. A denoising method comprising the steps of:
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generating, based on a digital image acquired by imaging a subject, a plurality of band-limited images respectively representing components of a plurality of frequency bands of said digital image;
obtaining a plurality of converted images by performing on respective pixel values of said band-limited images a nonlinear conversion process, in which an absolute value of an output value is reduced to an absolute value of an input value or less, and in which, for an input value whose absolute value is a predetermined threshold value or less, an absolute value of an output value becomes greater as an absolute value of said input value becomes greater and, for an input value whose absolute value is greater than said predetermined value, an absolute value of an output value becomes less than or equal to an absolute value of an output value corresponding to said predetermined threshold value;
multiplying the pixel values of said converted images by a predetermined subtraction coefficient; and
obtaining a pixel value of a processed image by subtracting the pixel values of said converted images multiplied by said predetermined subtraction coefficient, from a pixel value of said digital image. - View Dependent Claims (2, 3, 4, 5)
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6. A denoising apparatus comprising:
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band-limited image generating means for generating, based on a digital image acquired by imaging a subject, a plurality of band-limited images respectively representing components of a plurality of frequency bands of said digital image;
nonlinear conversion means for obtaining a plurality of converted images by performing on respective pixel values of said band-limited images a nonlinear conversion process, in which an absolute value of an output value is reduced to an absolute value of an input value or less, and in which, for an input value whose absolute value is a predetermined threshold value or less, an absolute value of an output value becomes greater as an absolute value of said input value becomes greater and, for an input value whose absolute value is greater than said predetermined value, an absolute value of an output value becomes less than or equal to an absolute value of an output value corresponding to said predetermined threshold value; and
frequency inhibition means for multiplying the pixel values of said converted images by a predetermined subtraction coefficient, and for obtaining a pixel value of a processed image by subtracting the pixel values of said converted images multiplied by said predetermined subtraction coefficient, from a pixel value of said digital image. - View Dependent Claims (7, 8, 9, 10)
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11. A program for causing a computer to carry out:
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a process of generating, based on a digital image acquired by imaging a subject, a plurality of band-limited images respectively representing components of a plurality of frequency bands of said digital image;
a process of obtaining a plurality of converted images by performing on respective pixel values of said band-limited images a nonlinear conversion process in which an absolute value of an output value is reduced to an absolute value of an input value or less, and in which, for an input value whose absolute value is a predetermined threshold value or less, an absolute value of an output value becomes greater as an absolute value of said input value becomes greater and, for an input value whose absolute value is greater than said predetermined value, an absolute value of an output value becomes less than or equal to an absolute value of an output value corresponding to said predetermined threshold value;
a process of multiplying the pixel values of said converted images by a predetermined subtraction coefficient; and
a process of obtaining a pixel value of a processed image by subtracting the pixel values of said converted images multiplied by said predetermined subtraction coefficient, from a pixel value of said digital image.
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Specification