Claims
- 1. A method of processing a digital image, comprising the steps of:
providing digital data indexed to represent positions of an image having S spectral bands for simultaneous output on a display, said digital data being indicative of an intensity value Ii(x,y) for each position (x,y) in each i-th spectral band; defining a classification of said image based on dynamic range of said image in each of said S spectral bands; adjusting said intensity value for said each position in each i-th spectral band to generate an adjusted intensity value for said each position in each i-th spectral band in accordance with 9∑n=1NWn(log Ii(x,y)-log[Ii(x,y)*Fn(x,y)]),i=1,…,Swhere S is the number of unique spectral bands included in said digital data and, for each n, Wn is a weighting factor and Fn(x,y) is a unique surround function applied to said each position (x,y) and N is the total number of unique surround functions; and filtering said adjusted intensity value for said each position of said image in each of said S spectral bands using a filter function based on said classification of said image wherein a filtered intensity value Ri(x,y) is defined.
- 2. A method according to claim 1 wherein each said unique surround function is a Gaussian function.
- 3. A method according to claim 2 wherein said Gaussian function is of the form
- 4. A method according to claim 1 further comprising the step of multiplying said filtered intensity value Ri(x,y) by
- 5. A method according to claim 1 wherein said each position (x,y) defines a pixel of said display.
- 6. A method according to claim 1 wherein, for each n, Wn=1/N.
- 7. A method according to claim 1 wherein said step of defining comprises the step of using image statistics associated with said image in each of said S spectral bands to select said filter function.
- 8. A method according to claim 7 wherein said image statistics include brightness and contrast of said image in each of said S spectral bands.
- 9. A method according to claim 1 further comprising the steps of:
selecting a maximum intensity value Vi(x,y) from the group consisting of said intensity value Ii(x,y) and said filtered intensity value Ri(x,y); and displaying an improved image using said maximum intensity value Vi(x,y).
- 10. A method according to claim 4 further comprising the steps of:
selecting a maximum intensity value Vi(x,y) from the group consisting of said intensity value Ii(x,y) and said color-restored intensity value R′i(x,y); and displaying an improved image using said maximum intensity value Vi(x,y).
- 11. A method of processing a digital image, comprising the steps of:
providing digital data indexed to represent the positions of a plurality of pixels of a J-row by K-column display, said digital data being indicative of an intensity value I(x,y) for each of said plurality of pixels where x is an index of a position in the J-th row of said display and y is an index of a position in the K-th column of said display wherein a J×K image is defined; convolving said digital data associated with each of said plurality of pixels with a function 13e-r2c2to form a discrete convolution value for each of said plurality of pixels, said function satisfying the relationship 14k∫∫e-r2c2ⅆxⅆy=1wherer={square root}{square root over (x2+y2)}k is a normalization constant and c is a constant; converting, for each of said plurality of pixels, said discrete convolution value into the logarithm domain; converting, for each of said plurality of pixels, said intensity value into the logarithm domain; subtracting, for each of said plurality of pixels, said discrete convolution value so-converted into the logarithm domain from said intensity value so-converted into the logarithm domain, wherein an adjusted intensity value is generated for each of said plurality of pixels; and filtering said adjusted intensity value for each of said plurality of pixels with a filter function that is based on dynamic range of said J×K image wherein a filtered intensity value R(x,y) is defined.
- 12. A method according to claim 11 wherein the value of said constant c is selected to be in the range of approximately 0.01 to approximately 0.5 of the larger of J and K.
- 13. A method according to claim 11 further comprising the steps of:
selecting, for each of said plurality of pixels, a maximum intensity value V(x,y) from the group consisting of said intensity value I(x,y) and said filtered intensity value R(x,y); and displaying an improved image using said maximum intensity value V(x,y).
- 14. A method of processing a digital image, comprising the steps of:
providing digital data indexed to represent the positions of a plurality of pixels of an J-row by K-column display, said digital data being indicative of an intensity value Ii(x,y) for each i-th spectral band of S spectral bands for each of said plurality of pixels where x is an index of a position in the J-th row of said display and y is an index of a position in the K-th column of said display wherein a (J×K)i image is defined for each of said S spectral bands and a J×K image is defined across all of said S spectral bands; defining a classification of said J×K image based on dynamic range of each said (J×K)i; convolving said digital data associated with each of said plurality of pixels in each i-th spectral band with a function 15e-r2cn2for n=2 to N to form N convolution values for each of said plurality of pixels in each said i-th spectral band, said function satisfying the relationship 16kn∫∫e-r2cn2ⅆxⅆy=1wherer={square root}{square root over (x2+y2)}and, for each n, kn is a normalization constant and cn is a unique constant; converting, for each of said plurality of pixels in each said i-th spectral band, each of said N convolution values into the logarithm domain; converting, for each of said plurality of pixels in each said i-th spectral band, said intensity value into the logarithm domain; subtracting, for each of said plurality of pixels in each said i-th spectral band, each of said N convolution values so-converted into the logarithm domain from said intensity value so-converted into the logarithm domain, wherein an adjusted intensity value is generated for each of said plurality of pixels in each said i-th spectral band based on each of said N convolution values; forming a weighted sum for each of said plurality of pixels in each said i-th spectral band using said adjusted intensity values; and filtering said weighted sum for each of said plurality of pixels in each said i-th spectral band with a filter function that is based on said classification of said J×K image wherein a filtered intensity value Ri(x,y) is defined.
- 15. A method according to claim 14 wherein the value for each said unique constant cn is selected to be in the range of approximately 0.01 to approximately 0.5 of the larger of J and K.
- 16. A method according to claim 14 further comprising the step of multiplying said filtered intensity value Ri(x,y) by
- 17. A method according to claim 14 wherein said step of defining comprises the step of using image statistics associated with each said (J×K)i image to select said filter function.
- 18. A method according to claim 17 wherein said image statistics include brightness and contrast of each said (J×K)i image.
- 19. A method according to claim 14 further comprising the steps of:
selecting a maximum intensity value Vi(x,y) from the group consisting of said intensity value Ii(x,y) and said filtered intensity value Ri(x,y); and displaying an improved image using said maximum intensity value Vi(x,y).
- 20. A method according to claim 16 further comprising the steps of:
selecting a maximum intensity value Vi(x,y) from the group consisting of said intensity value Ii(x,y) and said color-restored intensity value R′i(x,y); and displaying an improved image using said maximum intensity value Vi(x,y).
- 21. A method of processing a digital image, comprising the steps of:
providing digital data indexed to represent positions of an image having S spectral bands for simultaneous output on a display, said digital data being indicative of an intensity value I1(x,y) for each position (x,y) in each i-th spectral band; defining a classification of said image based on dynamic range of said image in each of said S spectral bands; adjusting said intensity value for said each position in each i-th spectral band to generate an adjusted intensity value for said each position in each i-th spectral band in accordance with 18∑n=1NWn(log Ii(x,y)-log[Ii(x,y)*Fn(x,y)]),i=1, ,Swhere S is a whole number greater than or equal to 2 and defines the total number of spectral bands included in said digital data and, for each n, Wn is a weighting factor and Fn(x,y) is a unique surround function of the form 19e-r2cn2satisfying the relationship 20kn∫∫e-r2cn2ⅆxⅆy=1wherer={square root}{square root over (x2+y2)}and, for each n, kn is a normalization constant and cn is a unique constant where N is the total number of unique surround functions; filtering said adjusted intensity value for said each position in each i-th spectral band with a function based on said classification of said image wherein a filtered intensity value Ri(x,y) is defined; and multiplying said filtered intensity value Ri(x,y) by 21log [BIi(x,y)∑i=1S Ii(x,y)]to define a color-restored intensity value R′i(x,y), where B is a constant.
- 22. A method according to claim 21 wherein, for each n, Wn=1/N.
- 23. A method according to claim 21 wherein the value for each said unique constant cn is selected to be in the range of approximately 0.01 to approximately 0.5 of the larger of J and K.
- 24. A method according to claim 21 wherein said step of defining comprises the step of using image statistics associated with said image in each of said S spectral bands to select said filter function.
- 25. A method according to claim 24 wherein said image statistics include brightness and contrast of said image in each of said S spectral bands.
- 26. A method according to claim 21 further comprising the steps of:
selecting a maximum intensity value Vi(x,y) from the group consisting of said intensity value Ii(x,y) and said color-restored intensity value R′i(x,y); and displaying an improved image using said maximum intensity value Vi(x,y).
STATEMENT OF GOVERNMENT INTEREST
[0001] This invention was made with Government support under contract NCC-1-258 awarded by NASA. The Government has certain rights in this invention.