Systems and methods for contrast adjustment
OwnerAnoop Bhattacharjyainventor
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Abstract
Systems and methods are disclosed that obtain detail information of an input image by employing multiple filters that present multi-resolution views of the image data. In embodiments, systems and methods perform contrast adjustment by employing a plurality of edge-preserving adaptive filters (EPAF), which generate images at multiple levels of resolution. An edge-preserving adaptive filter comprises a set of filters comprising a set of spatial filters with the same kernel size but with differing spatial orientations. For an input pixel value that is filtered, each of the plurality of edge-preserving adaptive filters outputs the filtered pixel value obtained from its set of filters that has the smallest numerical difference from the input pixel value.
Claims20
A method for performing contrast adjustment of an input image comprising a plurality of input pixels each having a value, the method comprising the steps of:
- applying, to the input image, a plurality of edge-preserving adaptive filters, each comprising a set of filters comprising a set of spatial filters with differing spatial orientations and with a kernel size differing from the other edge-preserving adaptive filters' sets of spatial filters;
- and
- wherein, for an input pixel value that is filtered, each of the plurality of edge-preserving adaptive filters outputs the filtered pixel value obtained from its set of filters that has the smallest numerical difference from the input pixel value.
A method for performing contrast adjustment of an input image comprising a plurality of input pixels each having a value, the method comprising the steps of:
- applying a first edge-preserving adaptive filter comprising a first set of spatial filters with differing spatial orientations and with a first region of support to an input pixel value to obtain a first set of filtered pixel values and selecting a first filtered pixel value from the first set of filtered pixel values that has a value closest to the input pixel value;
- applying a second edge-preserving adaptive filter comprising a second set of spatial filters with differing spatial orientations and with a second region of support to the input pixel value to obtain a second set of filtered pixel values and selecting a second filtered pixel value from the second set of filtered pixel values that has a value closest to the input pixel value;
- obtaining a difference pixel value by subtracting the second filtered pixel value from the first filtered pixel value;
- applying a clipping function to the difference pixel value to obtain a clipped pixel value;
- adjusting the clipped pixel value by a gain factor to obtain an adjusted pixel value;
- applying a largest edge-preserving adaptive filter comprising a set of spatial filters with differing spatial orientations and with a largest region of support to the input pixel value to obtain a set of filtered pixel values and selecting a filtered pixel value from the set of filtered pixel values that has a value closest to the input pixel value and applying a contrast stretching function to the filtered pixel value to obtain a stretched pixel value;
- and
- adding the adjusted pixel value to the stretched pixel value.
A system for performing contrast adjustment of an input image comprising a plurality of input pixels each having a value, the system comprising:
- a plurality of edge-preserving adaptive filters coupled to receive the input image, said edge-preserving adaptive filters each comprising a set of filters comprising a set of spatial filters with differing spatial orientations and with a kernel size differing from the other edge-preserving adaptive filters' sets of spatial filters;
- and
- wherein, for an input pixel value that is filtered, each of the plurality of edge-preserving adaptive filters outputs the filtered pixel value obtained from its set of filters that has the smallest numerical difference from the input pixel value.
Dependencies are inferred from the claim text.