Method and apparatus for compressing dynamic ranges of images

Claim 1

A method for compressing a dynamic range of an image, comprising the steps of: i) calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) changing the rate of compression, at which the dynamic range of the original image is compressed, in accordance with the unsharp mask signal Lu, and iii) carrying out a dynamic range compressing process with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) where f(Lu) is a function of Lu, a processed image signal Dproc being thereby obtained, wherein the unsharp mask signal Lu represents the mean value of the image signal values of all picture elements located within a rectangular unsharp mask having shorter sides, which extend across an edge of a region of interest in the original image, and longer sides extending in the direction along which the edge extends.

Claim 2

A method for compressing a dynamic range of an image, comprising the steps of: i) calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) changing the rate of compression, at which the dynamic range of the original image is compressed, in accordance with the unsharp mask signal Lu, and iii) carrying out a dynamic range compressing process with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) where f(Lu) is a function of Lu, a processed image signal Dproc being thereby obtained, wherein the unsharp mask signal Lu represents the mean value of the image signal values of all picture elements located within a rectangular unsharp mask having shorter sides, which extend across an edge of a region of interest in the original image, and longer sides extending in the direction along which the edge extends.

Claim 8

A method for compressing a dynamic range of an image, comprising the steps of: i) calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) changing the rate of compression, at which the dynamic range of the original image is compressed, in accordance with the unsharp mask signal Lu, and iii) carrying out a dynamic range compressing process with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) where f(Lu) is a function of Lu, a processed image signal Dproc being thereby obtained, wherein the unsharp mask signal Lu represents the mean value calculated from only the image signal values, which are among the image signal values of all picture elements located within an unsharp mask, that is set in order to obtain the unsharp mask signal Lu, and the differences of which from the image signal value of a middle picture element in the unsharp mask are not larger than a predetermined threshold value.

Claim 9

A method for compressing a dynamic range of an image, comprising the steps of: i) calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) changing the rate of compression, at which the dynamic range of the original image is compressed, in accordance with the unsharp mask signal Lu, and iii) carrying out a dynamic range compressing process with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) where f(Lu) is a function of Lu, a processed image signal Dproc being thereby obtained, wherein the unsharp mask signal Lu represents the mean value calculated from only the image signal values, which are among the image signal values of all picture elements located within an unsharp mask, that is set in order to obtain the unsharp mask signal Lu, and the differences of which from the image signal value of a middle picture element in the unsharp mask are not larger than a predetermined threshold value.

Claim 15

A method for compressing a dynamic range of an image, comprising the steps of: i) calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) changing the rate of compression, at which the dynamic range of the original image is compressed, in accordance with the unsharp mask signal Lu, and iii) carrying out a dynamic range compressing process with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) where f(Lu) is a function of Lu, a processed image signal Dproc being thereby obtained, wherein as for the image signal values, which are among the image signal values of all picture elements located within an unsharp mask, that is set in order to obtain the unsharp mask signal Lu, and the differences of which from the image signal value of a middle picture element in the unsharp mask are not larger than a predetermined threshold value, the image signal values are used directly as the image signal values for the calculation of the unsharp mask signal Lu, as for the image signal values, which are among the image signal values of all picture elements located within the unsharp mask, and the differences of which from the image signal value of the middle picture element in the unsharp mask are larger than the predetermined threshold value, the predetermined threshold value is used as the image signal values for the calculation of the unsharp mask signal Lu, and the mean value calculated from the image signal values for the calculation of the unsharp mask signal Lu is taken as the value of the unsharp mask signal Lu.

Claim 16

A method for compressing a dynamic range of an image, comprising the steps of: i) calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) changing the rate of compression, at which the dynamic range of the original image is compressed, in accordance with the unsharp mask signal Lu, and iii) carrying out a dynamic range compressing process with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) where f(Lu) is a function of Lu, a processed image signal Dproc being thereby obtained, wherein as for the image signal values, which are among the image signal values of all picture elements located within an unsharp mask, that is set in order to obtain the unsharp mask signal Lu, and the differences of which from the image signal value of a middle picture element in the unsharp mask are not larger than a predetermined threshold value, the image signal values are used directly as the image signal values for the calculation of the unsharp mask signal Lu, as for the image signal values, which are among the image signal values of all picture elements located within the unsharp mask, and the differences of which from the image signal value of the middle picture element in the unsharp mask are larger than the predetermined threshold value, the predetermined threshold value is used as the image signal values for the calculation of the unsharp mask signal Lu, and the mean value calculated from the image signal values for the calculation of the unsharp mask signal Lu is taken as the value of the unsharp mask signal Lu.

Claim 22

A method for compressing a dynamic range of an image, comprising the steps of: i) carrying out a morphology operation on an original image signal Dorg, which represents an original image, the morphology operation being carried out with Formula (2) or Formula (3) by using a structure element Bi, which is larger than a spatial fluctuation range of image signal values corresponding to an image portion representing an unnecessary tissue or noise in the original image, and a scale factor λ, a morphology signal Dmor being obtained from the morphology operation, ##EQU7## wherein the expression X ⊖ λY represents that λ times of calculations for finding the Minkowski difference are carried out with the structure element Y on the image signal X, and the expression X ⊕ λY represents that λ times of calculations for finding the Minkowski sum are carried out with the structure element Y on the image signal X, ##EQU8## wherein the expression X ⊕ λY represents that λ times of calculations for finding the Minkowski sum are carried out with the structure element Y on the image signal X, and the expression X E) λY represents that λ calculations for finding the Minkowski difference are carried out with the structure element Y on the image signal X, ii) changing the rate of compression, at which the dynamic range of the original image is compressed, in accordance with the morphology signal Dmor having been obtained from the morphology operation, and iii) carrying out a dynamic range compressing process with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements, the dynamic range compressing process being carried out with Formula (4) Dproc=Dorg+f(Dmor) (4) where f(Dmor) is a function of Dmor, a processed image signal Dproc being thereby obtained.

Claim 23

A method for compressing a dynamic range of an image, comprising the steps of: i) carrying out a morphology operation on an original image signal Dorg, which represents an original image, the morphology operation being carried out with Formula (2) or Formula (3) by using a structure element Bi, which is larger than a spatial fluctuation range of image signal values corresponding to an image portion representing an unnecessary tissue or noise in the original image, and a scale factor λ, a morphology signal Dmor being obtained from the morphology operation, ##EQU7## wherein the expression X ⊖ λY represents that λ times of calculations for finding the Minkowski difference are carried out with the structure element Y on the image signal X, and the expression X ⊕ λY represents that λ times of calculations for finding the Minkowski sum are carried out with the structure element Y on the image signal X, ##EQU8## wherein the expression X ⊕ λY represents that λ times of calculations for finding the Minkowski sum are carried out with the structure element Y on the image signal X, and the expression X E) λY represents that λ calculations for finding the Minkowski difference are carried out with the structure element Y on the image signal X, ii) changing the rate of compression, at which the dynamic range of the original image is compressed, in accordance with the morphology signal Dmor having been obtained from the morphology operation, and iii) carrying out a dynamic range compressing process with respect to each of picture elements in the original image, with the rate of compression being thus changed for each of the picture elements, the dynamic range compressing process being carried out with Formula (4) Dproc=Dorg+f(Dmor) (4) where f(Dmor) is a function of Dmor, a processed image signal Dproc being thereby obtained.

Claim 29

An apparatus for compressing a dynamic range of an image, comprising: i) an unsharp mask signal calculating means for calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) a compression rate determining function storage means for storing information about a function representing the rate of compression f(Lu), at which the dynamic range of the original image is compressed, the unsharp mask signal Lu, which has been obtained from the unsharp mask signal calculating means, serving as a variable in the function f(Lu), and iii) a dynamic range compressing operation means for carrying out a dynamic range compressing process with respect to each of picture elements in the original image, by using the rate of compression f(Lu) for each of the picture elements, which rate of compression is obtained in accordance with the function stored in the compression rate determining function storage means, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) a processed image signal Dproc being thereby obtained, wherein the unsharp mask signal calculating means calculates, as the unsharp mask signal Lu, the mean value of the image signal values of all picture elements located within a rectangular unsharp mask having shorter sides, which extend across an edge of the region of interest in the original image, and longer sides extending in the direction along which the edge extends.

Claim 30

An apparatus for compressing a dynamic range of an image, comprising: i) an unsharp mask signal calculating means for calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) a compression rate determining function storage means for storing information about a function representing the rate of compression f(Lu), at which the dynamic range of the original image is compressed, the unsharp mask signal Lu, which has been obtained from the unsharp mask signal calculating means, serving as a variable in the function f(Lu), and iii) a dynamic range compressing operation means for carrying out a dynamic range compressing process with respect to each of picture elements in the original image, by using the rate of compression f(Lu) for each of the picture elements, which rate of compression is obtained in accordance with the function stored in the compression rate determining function storage means, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) a processed image signal Dproc being thereby obtained, wherein the unsharp mask signal calculating means calculates, as the unsharp mask signal Lu, the mean value of the image signal values of all picture elements located within a rectangular unsharp mask having shorter sides, which extend across an edge of the region of interest in the original image, and longer sides extending in the direction along which the edge extends.

Claim 36

An apparatus for compressing a dynamic range of an image, comprising: i) an unsharp mask signal calculating means for calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) a compression rate determining function storage means for storing information about a function representing the rate of compression f(Lu), at which the dynamic range of the original image is compressed, the unsharp mask signal Lu, which has been obtained from the unsharp mask signal calculating means, serving as a variable in the function f(Lu), and iii) a dynamic range compressing operation means for carrying out a dynamic range compressing process with respect to each of picture elements in the original image, by using the rate of compression f(Lu) for each of the picture elements, which rate of compression is obtained in accordance with the function stored in the compression rate determining function storage means, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) a processed image signal Dproc being thereby obtained, wherein the unsharp mask signal calculating means calculates, as the unsharp mask signal Lu, the mean value calculated from only the image signal values, which are among the image signal values of all picture elements located within an unsharp mask, that is set in order to obtain the unsharp mask signal Lu, and the differences of which from the image signal value of a middle picture element in the unsharp mask are not larger than a predetermined threshold value.

Claim 37

An apparatus for compressing a dynamic range of an image, comprising: i) an unsharp mask signal calculating means for calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) a compression rate determining function storage means for storing information about a function representing the rate of compression f(Lu), at which the dynamic range of the original image is compressed, the unsharp mask signal Lu, which has been obtained from the unsharp mask signal calculating means, serving as a variable in the function f(Lu), and iii) a dynamic range compressing operation means for carrying out a dynamic range compressing process with respect to each of picture elements in the original image, by using the rate of compression f(Lu) for each of the picture elements, which rate of compression is obtained in accordance with the function stored in the compression rate determining function storage means, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) a processed image signal Dproc being thereby obtained, wherein the unsharp mask signal calculating means calculates, as the unsharp mask signal Lu, the mean value calculated from only the image signal values, which are among the image signal values of all picture elements located within an unsharp mask, that is set in order to obtain the unsharp mask signal Lu, and the differences of which from the image signal value of a middle picture element in the unsharp mask are not larger than a predetermined threshold value.

Claim 43

An apparatus for compressing a dynamic range of an image, comprising: i) an unsharp mask signal calculating means for calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) a compression rate determining function storage means for storing information about a function representing the rate of compression f(Lu), at which the dynamic range of the original image is compressed, the unsharp mask signal Lu, which has been obtained from the unsharp mask signal calculating means, serving as a variable in the function f(Lu), and iii) a dynamic range compressing operation means for carrying out a dynamic range compressing process with respect to each of picture elements in the original image, by using the rate of compression f(Lu) for each of the picture elements, which rate of compression is obtained in accordance with the function stored in the compression rate determining function storage means, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) a processed image signal Dproc being thereby obtained, wherein as for the image signal values, which are among the image signal values of all picture elements located within an unsharp mask, that is set in order to obtain the unsharp mask signal Lu, and the differences of which from the image signal value of a middle picture element in the unsharp mask are not larger than a predetermined threshold value, the image signal values are used directly as the image signal values for the calculation of the unsharp mask signal Lu, as for the image signal values, which are among the image signal values of all picture elements located within the unsharp mask, and the differences of which from the image signal value of the middle picture element in the unsharp mask are larger than the predetermined threshold value, the predetermined threshold value is used as the image signal values for the calculation of the unsharp mask signal Lu, and the unsharp mask signal calculating means calculates, as the unsharp mask signal Lu, the mean value calculated from the image signal values for the calculation of the unsharp mask signal Lu.

Claim 44

An apparatus for compressing a dynamic range of an image, comprising: i) an unsharp mask signal calculating means for calculating an unsharp mask signal Lu, which corresponds to super-low frequency, from an original image signal Dorg representing an original image, ii) a compression rate determining function storage means for storing information about a function representing the rate of compression f(Lu), at which the dynamic range of the original image is compressed, the unsharp mask signal Lu, which has been obtained from the unsharp mask signal calculating means, serving as a variable in the function f(Lu), and iii) a dynamic range compressing operation means for carrying out a dynamic range compressing process with respect to each of picture elements in the original image, by using the rate of compression f(Lu) for each of the picture elements, which rate of compression is obtained in accordance with the function stored in the compression rate determining function storage means, the dynamic range compressing process being carried out with Formula (1) Dproc=Dorg+f(Lu) (1) a processed image signal Dproc being thereby obtained, wherein as for the image signal values, which are among the image signal values of all picture elements located within an unsharp mask, that is set in order to obtain the unsharp mask signal Lu, and the differences of which from the image signal value of a middle picture element in the unsharp mask are not larger than a predetermined threshold value, the image signal values are used directly as the image signal values for the calculation of the unsharp mask signal Lu, as for the image signal values, which are among the image signal values of all picture elements located within the unsharp mask, and the differences of which from the image signal value of the middle picture element in the unsharp mask are larger than the predetermined threshold value, the predetermined threshold value is used as the image signal values for the calculation of the unsharp mask signal Lu, and the unsharp mask signal calculating means calculates, as the unsharp mask signal Lu, the mean value calculated from the image signal values for the calculation of the unsharp mask signal Lu.

Claim 50

An apparatus for compressing a dynamic range of an image, comprising: i) a morphology signal operation means for carrying out a morphology operation on an original image signal Dorg, which represents an original image, the morphology operation being carried out with Formula (2) or Formula (3) by using a structure element Bi, which is larger than a spatial fluctuation range of image signal values corresponding to an image portion representing an unnecessary tissue or noise in the original image, and a scale factor λ, a morphology signal Dmor, which is represented by Formula (2) or Formula (3), being obtained from the morphology signal operation means, ##EQU9## wherein the expression X ⊖ λY represents that λ times of calculations for finding the Minkowski difference are carried out with the structure element Y on the image signal X, and the expression X ⊕ λY represents that λ times of calculations for finding the Minkowski sum are carried out with the structure element Y on the image signal X, ##EQU10## wherein the expression X ⊕ λY represents that λ times of calculations for finding the Minkowski sum are carried out with the structure element Y on the image signal X, and the expression X ⊖ λY represents that λ times of calculations for finding the Minkowski difference are carried out with the structure element Y on the image signal X, ii) a compression rate determining function storage means for storing information about a function representing the rate of compression f(Dmor), at which the dynamic range of the original image is compressed, the morphology signal Dmor, which has been obtained from the morphology signal operation means, serving as a variable in the function f(Dmor), and iii) a dynamic range compressing operation means for carrying out a dynamic range compressing process with respect to each of picture elements in the original image, by using the rate of compression f(Dmor) for each of the picture elements, which rate of compression is obtained in accordance with the function stored in the compression rate determining function storage means, the dynamic range compressing process being carried out with Formula (4) Dproc=Dorg+f(Dmor) (4) a processed image signal Dproc being thereby obtained.

Claim 51

An apparatus for compressing a dynamic range of an image, comprising: i) a morphology signal operation means for carrying out a morphology operation on an original image signal Dorg, which represents an original image, the morphology operation being carried out with Formula (2) or Formula (3) by using a structure element Bi, which is larger than a spatial fluctuation range of image signal values corresponding to an image portion representing an unnecessary tissue or noise in the original image, and a scale factor λ, a morphology signal Dmor, which is represented by Formula (2) or Formula (3), being obtained from the morphology signal operation means, ##EQU9## wherein the expression X ⊖ λY represents that λ times of calculations for finding the Minkowski difference are carried out with the structure element Y on the image signal X, and the expression X ⊕ λY represents that λ times of calculations for finding the Minkowski sum are carried out with the structure element Y on the image signal X, ##EQU10## wherein the expression X ⊕ λY represents that λ times of calculations for finding the Minkowski sum are carried out with the structure element Y on the image signal X, and the expression X ⊖ λY represents that λ times of calculations for finding the Minkowski difference are carried out with the structure element Y on the image signal X, ii) a compression rate determining function storage means for storing information about a function representing the rate of compression f(Dmor), at which the dynamic range of the original image is compressed, the morphology signal Dmor, which has been obtained from the morphology signal operation means, serving as a variable in the function f(Dmor), and iii) a dynamic range compressing operation means for carrying out a dynamic range compressing process with respect to each of picture elements in the original image, by using the rate of compression f(Dmor) for each of the picture elements, which rate of compression is obtained in accordance with the function stored in the compression rate determining function storage means, the dynamic range compressing process being carried out with Formula (4) Dproc=Dorg+f(Dmor) (4) a processed image signal Dproc being thereby obtained.