Method and apparatus for area selective exposure adjustment
First Claim
1. A method for processing a digital image having a dynamic range representing a brightness in an original scene greater than the dynamic range of an output medium, comprising the steps of:
- a) dividing the image into first and second portions, the first portion of the image representing a brightness range extending from a minimum brightness up to a distance equal to the dynamic range of the output medium, the second portion of the image representing a brightness range extending from a maximum brightness down to a distance equal to the dynamic range of the output medium;
b) determining first and second transformations for the first and second portions of the image respectively that map the first and second portions onto the dynamic range of the output medium using an exposure determination algorithm;
c) thresholding the digital image at a brightness level that divides the image into a first region having the lowest levels of brightness and a second region having the highest levels of brightness; and
d) applying the first transformation to the first region of the image and the second transformation to the second region of the image.
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Abstract
A digital image having a dynamic range representing a brightness in an original scene greater than the dynamic range of an output medium, is processed to fit the dynamic range of the output medium by dividing the image into first and second portions, the first portion of the image representing a brightness range extending from a minimum brightness up to a distance equal to the dynamic range of the output medium, the second portion of the image representing a brightness range extending from a maximum brightness down to a distance equal to the dynamic range of the output medium. First and second transformations are determined for the first and second portions of the image respectively that map the first and second portions onto the dynamic range of the output medium using a exposure determination algorithm of the type used in photographic printers. The digital image is then thresholded at a brightness level that divides the image into a first region having the lowest levels of brightness and a second region having the highest levels of brightness. Finally, the first transformation is applied to the first region of the image and the second transformation is applied to the second region of the image to produce a digital image having a dynamic range that matches the dynamic range of the output medium while maintaining natural contrast within objects in the image.
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Citations
17 Claims
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1. A method for processing a digital image having a dynamic range representing a brightness in an original scene greater than the dynamic range of an output medium, comprising the steps of:
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a) dividing the image into first and second portions, the first portion of the image representing a brightness range extending from a minimum brightness up to a distance equal to the dynamic range of the output medium, the second portion of the image representing a brightness range extending from a maximum brightness down to a distance equal to the dynamic range of the output medium; b) determining first and second transformations for the first and second portions of the image respectively that map the first and second portions onto the dynamic range of the output medium using an exposure determination algorithm; c) thresholding the digital image at a brightness level that divides the image into a first region having the lowest levels of brightness and a second region having the highest levels of brightness; and d) applying the first transformation to the first region of the image and the second transformation to the second region of the image. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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Specification