Image contrast enhancement
First Claim
Patent Images
1. A method for contrast enhancement for digital images, comprising:
- filtering an original image having original pixel color values, to generate a first filtered image corresponding to bright color values, and a second filtered image corresponding to dark color values;
receiving parameters for a brightening response curve, the brightening response curve being a function of the entire range of pixel color values that is user-adjustable;
receiving parameters for a darkening response curve, the darkening response curve being a function of the entire range of pixel color values that is user-adjustable;
deriving local brightening multipliers by applying the brightening response curve to the first filtered image;
deriving local darkening offsets and local darkening multipliers by applying the darkening response curve to the second filtered image; and
processing the original image, comprising;
subtracting the local darkening offsets from the original pixel color values to generate shifted color values;
multiplying the shifted color values by the local brightening multipliers; and
further multiplying the shifted color values by the local darkening multipliers, thereby generating a contrast-enhanced image from the original image.
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Accused Products
Abstract
A method for contrast enhancement for digital images, including filtering an original image having original color values, to generate a filtered image, receiving parameters for a response curve, the response curve being a function of color value that is user-adjustable, deriving local multipliers by applying the response curve to the filtered image, multiplying the original color values by the local multipliers, thereby generating a contrast-enhanced image from the original image. A system and a computer-readable storage medium are also described.
89 Citations
88 Claims
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1. A method for contrast enhancement for digital images, comprising:
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filtering an original image having original pixel color values, to generate a first filtered image corresponding to bright color values, and a second filtered image corresponding to dark color values; receiving parameters for a brightening response curve, the brightening response curve being a function of the entire range of pixel color values that is user-adjustable; receiving parameters for a darkening response curve, the darkening response curve being a function of the entire range of pixel color values that is user-adjustable; deriving local brightening multipliers by applying the brightening response curve to the first filtered image; deriving local darkening offsets and local darkening multipliers by applying the darkening response curve to the second filtered image; and processing the original image, comprising; subtracting the local darkening offsets from the original pixel color values to generate shifted color values; multiplying the shifted color values by the local brightening multipliers; and further multiplying the shifted color values by the local darkening multipliers, thereby generating a contrast-enhanced image from the original image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A system for enhancing contrast of digital images, comprising:
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a filter processor for filtering an original image having original pixel color values, to generate a first filtered image corresponding to bright color values, and a second filtered image corresponding to dark color values; a user interface (i) for receiving parameters for a brightening response curve, the brightening response curve being a function of the entire range of pixel color values that is user-adjustable, and (ii) for receiving parameters for a darkening response curve, the darkening response curve also being a function of the entire range of pixel color values that is user-adjustable; and an image enhancer coupled to said filter processor and to said user interface (i) for deriving local brightening multipliers by applying the brightening response curve to the first filtered image, (ii) for deriving local darkening offsets and local darkening multipliers by applying the darkening response curve to the second filtered image, (iii) for multiplying the original pixel color values by the local brightening multipliers to generated scaled color values, (iv) for subtracting the local darkening offsets from the scaled color values to generate shifted color values, and (v) for further multiplying the shifted color values by the local darkening multipliers, thereby generating a contrast-enhanced image from the original image. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image having original pixel color values, to generate a first filtered image corresponding to bright color values, and a second filtered image corresponding to dark color values; to receive parameters for a brightening response curve, the brightening response curve being a function of the entire range of pixel color values that is user-adjustable; to receive parameters for a darkening response curve, the darkening response curve being a function of the entire range of pixel color values that is user-adjustable; to derive local brightening multipliers by applying the brightness response curve to the first filtered image; to derive local darkening offsets and local darkening multipliers by applying the darkening response curve to the second filtered image; and to process the original image, comprising; to subtract the local darkening offsets from the original pixel color values to generate shifted color values; to multiply the shifted color values by the local brightening multipliers; and to further multiply the shifted color values by the local darkening multipliers, thereby generating a contrast-enhanced image from the original image.
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32. A method for contrast enhancement for digital images, comprising:
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filtering an original image having original pixel color values, to generate a first filtered image corresponding to bright color values, and a second filtered image corresponding to dark color values; receiving parameters for a brightening response curve, the brightening response curve being a function of the entire range of pixel color values that is user-adjustable; receiving parameters for a darkening response curve, the darkening response curve being a function of the entire range of pixel color values that is user-adjustable; deriving local brightening multipliers by applying the brightening response curve to the first filtered image; deriving local darkening offsets and local darkening multipliers by applying the darkening response curve to the second filtered image; and processing the original image, comprising; multiplying the original pixel color values by the local brightening multipliers to generate scaled color values; subtracting the local darkening offsets from the scaled color values to generate shifted color values; and multiplying the shifted color values by the local darkening multipliers, thereby generating a contrast-enhanced image from the original image.
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33. A system for enhancing contrast of digital images, comprising:
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a filter processor for filtering an original image having original pixel color values, to generate a first filtered image corresponding to bright color values, and a second filtered image corresponding to dark color values; a user interface (i) for receiving parameters for a brightening response curve, the brightening response curve being a function of the entire range of pixel color values that is user-adjustable, and (ii) for receiving parameters for a darkening response curve, the darkening response curve also being a function of the entire range of pixel color value values that is user-adjustable; and an image enhancer coupled to said filter processor and to said user interface (i) for deriving local brightening multipliers by applying the brightening response curve to the first filtered image, (ii) for deriving local darkening offsets and local darkening multipliers by applying the darkening response curve to the second filtered image, (iii) for subtracting the local darkening offsets from the original pixel color values to generate shifted color values, (iv) for multiplying the shifted color values by the local brightening multipliers, and (v) for further multiplying the shifted color values by the local darkening multipliers, thereby generating a contrast-enhanced image from the original image.
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34. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image having original pixel color values, to generate a first filtered image corresponding to bright color values, and a second filtered image corresponding to dark color values; to receive parameters for a brightening response curve, the brightening response curve being a function of the entire range of pixel color values that is user-adjustable; to receive parameters for a darkening response curve, the darkening response curve being a function of the entire range of pixel color values that is user-adjustable; to derive local brightening multipliers by applying the brightness response curve to the first filtered image; to derive local darkening offsets and local darkening multipliers by applying the darkening response curve to the second filtered image; and to process the original image, comprising; to multiply the original pixel color values by the local brightening multipliers to generate scaled color values; to subtract the local darkening offsets from the scaled color values to generate shifted color values; and to multiply the shifted color values by the local darkening multipliers, thereby generating a contrast-enhanced image from the original image.
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35. A method for contrast enhancement for digital images, comprising:
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filtering an original image having original pixel color values, to generate a filtered image; receiving parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; deriving local multipliers by applying the response curve to the filtered image; deriving local offset values from the local multipliers; and processing the original image, comprising; subtracting the local offset values from the original pixel color values to generate shifted color values; and multiplying the shifted color values by the local multipliers, thereby generating a contrast-enhanced image from the original image.
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36. A method for contrast enhancement for digital images, comprising:
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filtering an original image having original pixel color values, to generate a filtered image; receiving parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; deriving local multipliers by applying the response curve to the filtered image; deriving local offset values from the local multipliers; and processing the original image, comprising; multiplying the original pixel color values by the local multipliers to generate scaled color values; and subtracting the local offset values from the scaled color values, thereby generating a contrast-enhanced image from the original image.
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37. A method for contrast enhancement for digital images, comprising:
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filtering an original image having original pixel color values, to generate a filtered image; receiving parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; deriving local multipliers by applying the response curve to the filtered image; and multiplying the original pixel color values by the local multipliers, thereby generating a contrast-enhanced image from the original image.
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38. A system for enhancing contrast of digital images, comprising:
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a filter processor for filtering an original image having original pixel color values, to generate a filtered image; a user interface for receiving parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; and an image enhancer coupled to said filter processor and to said user interface (i) for deriving local multipliers by applying the response curve to the first filtered image, (ii) for deriving local offset values from the local multipliers, (iii) for subtracting the local offset values from the original pixel color values to generate shifted color values, and (iv) for multiplying the shifted color values by the local multipliers, thereby generating a contrast-enhanced image from the original image.
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39. A system for enhancing contrast of digital images, comprising:
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a filter processor for filtering an original image having original pixel color values, to generate a filtered image; a user interface for receiving parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; and an image enhancer coupled to said filter processor and to said user interface (i) for deriving local multipliers by applying the response curve to the first filtered image, (ii) for deriving local offset values from the local multipliers, (iii) for multiplying the original pixel color values by the local multipliers to generate scaled color values, and (iv) for subtracting the local offset values from the scaled color values, thereby generating a contrast-enhanced image from the original image.
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40. A system for enhancing contrast of digital images, comprising:
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a filter processor for filtering an original image having original pixel color values, to generate a filtered image; a user interface for receiving parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; and an image enhancer coupled to said filter processor and to said user interface (i) for deriving local multipliers by applying the response curve to the filtered image, and (ii) for multiplying the original pixel color values by the local multipliers, thereby generating a contrast-enhanced image from the original image.
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41. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image having original pixel color values, to generate a filtered image; to receive parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; to derive local multipliers by applying the response curve to the filtered image; to derive local offset values from the local multipliers; and to process the original image, comprising; to subtract the local offset values from the original pixel color values to generate shifted color values; and to multiply the shifted color values by the local multipliers, thereby generating a contrast-enhanced image from the original image.
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42. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image having original pixel color values, to generate a filtered image; to receive parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; to derive local multipliers by applying the response curve to the filtered image; to derive local offset values from the local multipliers; and to process the original image, comprising; to multiply the original pixel color values by the local multipliers to generate scaled color values; and to subtract the local offset values from the scaled color values, thereby generating a contrast-enhanced image from the original image.
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43. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image having original pixel color values, to generate a filtered image; to receive parameters for a response curve, the response curve being a function of the entire range of pixel color values that is user-adjustable; to derive local multipliers by applying the response curve to the filtered image; and to multiply the original pixel color values by the local multipliers, thereby generating a contrast-enhanced image from the original image.
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44. A method for contrast enhancement for digital images, comprising:
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filtering an original image, I, having original color values, to generate a first filtered image, Wb, corresponding to bright color values, and a second filtered image, Wd, corresponding to dark color values; receiving parameters for a brightening operation, the brightening operation being a function fb(W, I) that is user-adjustable; receiving parameters for a darkening operation, the darkening operation being a function fd(W, I) that is user-adjustable; and processing the original image by first darkening and then brightening, to obtain an enhanced image, Ienhanced, according to
Ienhanced=fb(Wb, fd(Wd, I)). - View Dependent Claims (45, 46, 47, 48, 49, 50, 51, 52)
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53. A method for contrast enhancement for digital images, comprising:
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filtering an original image, I, having original color values, to generate a first filtered image, Wb, corresponding to bright color values, and a second filtered image, Wd, corresponding to dark color values; receiving parameters for a brightening operation, the brightening operation being a function fb(W, I) that is user-adjustable; receiving parameters for a darkening operation, the darkening operation being a function fd(W, I) that is user-adjustable; and processing the original image by first brightening and then darkening to obtain an enhanced image, Ienhanced, according to
Ienhanced=fd(Wd, fb(Wb, I)).
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54. A system for enhancing contrast of digital images, comprising:
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a filter processor for filtering an original image, I, having original color values, to generate a first filtered image, Wb, corresponding to bright color values, and a second filtered image, Wd, corresponding to dark color values; a user interface (i) for receiving parameters for a brightening operation, the brightening operation being a function fb(W, I) that is user-adjustable, and (ii) for receiving parameters for a darkening operation, the darkening operation being a function fd(W, I) that is user-adjustable; and an image enhancer coupled to said filter processor and to said user interface for processing the original image by first brightening and then darkening to obtain an enhanced image, Ienhanced, according to
Ienhanced=fd(Wd, fb(WbI)). - View Dependent Claims (55, 56, 57, 58, 59, 60, 61, 62)
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63. A system for enhancing contrast of digital images, comprising:
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a filter processor for filtering an original image, I, having original color values, to generate a first filtered image, Wb, corresponding to bright color values, and a second filtered image, Wd, corresponding to dark color values; a user interface (i) for receiving parameters for a brightening operation, the brightening operation being a function fb(W, I) that is user-adjustable, and (ii) for receiving parameters for a darkening operation, the darkening operation being a function fd(W, I) that is user-adjustable; and an image enhancer coupled to said filter processor and to said user interface for processing the original image by first darkening and then brightening to obtain an enhanced image, Ienhanced, according to
Ienhanced=fb(Wb, fd(Wd, I)).
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64. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image, I, having original color values, to generate a first filtered image, Wb, corresponding to bright color values, and a second filtered image, Wd, corresponding to dark color values; to receive parameters for a brightening operation, the brightening operation being a function fb(W, I) that is user-adjustable; to receive parameters for a darkening operation, the darkening operation being a function fd(W, I) that is user-adjustable; and to process the original image by first darkening and then brightening, to obtain an enhanced image, Ienhanced, according to
Ienhanced=fb(Wb, fd(Wd, I)).
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65. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image, I, having original color values, to generate a first filtered image, Wb, corresponding to bright color values, and a second filtered image, Wd, corresponding to dark color values; to receive parameters for a brightening operation, the brightening operation being a function fb(W, I) that is user-adjustable; to receive parameters for a darkening operation, the darkening operation being a function fd(W, I) that is user-adjustable; and to process the original image by first brightening and then darkening, to obtain an enhanced image, Ienhanced, according to
Ienhanced=fb(Wb, fd(Wd, I)).
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66. A method for generating a response curve for image enhancement, comprising:
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receiving an original digital image, Isource, the digital image including an array of pixels, each pixel having a location and at least one color value, wherein each color value lies within an interval [0,S] ranging from a lower bound of 0 to an upper bound of S; selecting a basic shape function for a response curve, f, used to enhance the original image, the response curve including multipliers, f(V), for multiplying color values of the pixels from the original image Isource so as to generate an enhanced image, Ienhanced, where V itself is an array of pixel color values; and determining a multiplier, m, for the response curve f, such that if the response curve f is scaled by the multiplier m, then approximately a percentage, P, of the pixels in the resulting enhanced image Ienhanced have color values that fall out of the range [O,S], where the parameter P is a prescribed percentage. - View Dependent Claims (67, 68, 69, 70)
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71. A system for generating a response curve for image enhancement, comprising:
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a storage for storing an original digital image, Isource, the digital image including an array of pixels, each pixel having a location and at least one color value, wherein each color value lies within an interval [0,S] ranging from a lower bound of 0 to an upper bound of S; a response curve generator for selecting a basic shape function for a response curve, f, used to enhance the original image, the response curve including multipliers, f(V), for multiplying color values of the pixels from the original image Isource so as to generate an enhanced image, Ienhanced, where V itself is an array of pixel color values; and a statistical processor for determining a multiplier, m, for the response curve f, such that if the response curve f is scaled by the multiplier m, then approximately a percentage, P, of the pixels in the resulting enhanced image Ienhanced have color values that fall out of the range [0,S], where the parameter P is a prescribed percentage. - View Dependent Claims (72, 73, 74, 75)
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76. A non-transitory computer readable storage medium storing program code for causing a computer:
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to receive an original digital image, Isource, the digital image including an array of pixels, each pixel having a location and at least one color value, wherein each color value lies within an interval [O,S] ranging from a lower bound of O to an upper bound of S; to select a basic shape function for a response curve, f, used to enhance the original image, the response curve including multipliers, f(V), for multiplying color values of the pixels from the original image Isource so as to generate an enhanced image, Ienhanced, where V itself is an array of pixel color values; and to determine a multiplier, m, for the response curve f, such that if the response curve f is scaled by the multiplier m, then approximately a percentage, P, of the pixels in the resulting enhanced image Ienhanced have color values that fall out of the range [O,S], where the parameter P is a prescribed percentage.
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77. A method for enhancing contrast of digital images within a mobile image capture device, comprising:
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filtering an original image captured by a mobile image capture device, to generate a filtered image; deriving local contrast enhancement parameters by applying a response curve to the filtered image; and processing the original image by applying the local contrast enhancement parameters thereto, to generate a contrast-enhanced image.
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78. A method for enhancing contrast of digital images within a mobile image capture device, comprising:
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filtering an original image captured by a mobile image capture device, to generate a filtered original image; deriving local contrast enhancement parameters by applying a response curve to the filtered original image; processing the original image by applying the local contrast enhancement parameters thereto, to generate a contrast-enhanced image; storing the contrast-enhanced image within the mobile image capture device; and storing the response curve within the mobile image capture device, as meta-data of the contrast-enhanced image. - View Dependent Claims (79, 80)
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81. A system for enhancing contrast of digital images within a mobile image capture device, comprising:
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a filter processor housed within a mobile image capture device, for filtering an original image captured by the mobile image capture device, to generate a filtered image; and an image enhancer housed within the mobile image capture device and coupled with said filter processor, for (i) deriving local contrast enhancement parameters by applying a response curve to the filtered image, and (ii) processing the original image by applying the local contrast enhancement parameters thereto, to generate a contrast-enhanced image.
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82. A system for enhancing contrast of digital images within a mobile image capture device, comprising:
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a filter processor housed within a mobile image capture device, for filtering an original image captured by the mobile image capture device, to generate a filtered original image; an image enhancer housed within the mobile image capture device and coupled with said filter processor, for (i) deriving local contrast enhancement parameters by applying a response curve to the filtered original image, and (ii) processing the original image by applying the local contrast enhancement parameters thereto, to generate a contrast-enhanced image; and a memory housed within the mobile image capture device and coupled with said filter processor and said image enhancer, for storing (i) the contrast-enhanced image, and (ii) the response curve, as meta-data of the contrast-enhanced image. - View Dependent Claims (83, 84)
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85. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image captured by a mobile image capture device, to generate a filtered image; to derive local contrast enhancement parameters by applying a response curve to the filtered image; and to process the original image by applying the local contrast enhancement parameters thereto, to generate a contrast-enhanced image.
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86. A non-transitory computer readable storage medium storing program code for causing a computer:
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to filter an original image captured by a mobile image capture device, to generate a filtered image; to derive local contrast enhancement parameters by applying a response curve to the filtered image; to process the original image by applying the local contrast enhancement parameters thereto, to generate a contrast-enhanced image; to store the contrast-enhanced image within the mobile image capture device; and to store the response curve within the mobile image capture device, as meta-data of the contrast-enhanced image.
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87. A system for enhancing contrast of digital images, comprising:
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a server computer comprising; a filter processor for filtering an input image, Iinput, to generate a filtered image, Winput; an image enhancer for processing Iinput by brightening or darkening to obtain an enhanced image, Ioutput, according to
Ioutput=f(Winput, Iinput),where the function f is a brightening response curve or a darkening response curve; an image sub-sampler coupled with said image enhancer for processing an original high-resolution image to obtain a lower resolution image therefrom; a transmitter coupled with said image sub-sampler for transmitting a sub-sampled image to a client computer for display; and a receiver coupled with said image enhancer for receiving from the client computer at least one parameter p used to determine the function f; a client computer connected to said server computer via a computer network, comprising; a receiver for receiving a sub-sampled image from said server computer; a user interface coupled with said client receiver enabling a user to view the received sub-sampled image and to adjust the at least one parameter p, based on the appearance of the received sub-sampled image; and a transmitter coupled with said user interface for transmitting the adjusted at least one parameter p to said server computer.
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88. A system for enhancing contrast of digital images, comprising:
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a server computer comprising; a filter processor for filtering an original high-resolution image, I, to generate a filtered image, W; an image enhancer for processing the image I by brightening or darkening to obtain an enhanced image, Ienhanced, according to
Ienhanced=f(W, I),where the function f is a brightening response curve or a darkening response curve; an image sub-sampler coupled with said image enhancer for processing the original high-resolution image to obtain an original lower resolution image, Isub, therefrom; a transmitter coupled with said image sub-sampler for transmitting the original lower resolution image Isub to a client computer for processing; and a receiver coupled with said image enhancer for receiving the function f from the client computer; a client computer connected to said server computer via a computer network, comprising; a receiver for receiving the original lower resolution image Isub from said server computer; a filter processor for filtering the original lower resolution image Isub, to generate a filtered image, Wsub; an image enhancer (i) for setting and adjusting the function f, and (ii) for processing the image Isub by brightening or darkening to obtain an enhanced lower resolution image, Isub-enhanced, according to
Isub-enhanced=f(Wsub, Isub) ; anda transmitter coupled with said user interface for transmitting the function f to said server computer.
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Specification