Adaptive histogram-based video contrast enhancement
First Claim
1. A contrast enhancement system, comprising:
- a histogram updater configured to;
provide a histogram based on an image;
determine arithmetic means for at least two regions of the histogram; and
calculate variances for each of the determined arithmetic means;
a weighting factor calculator configured to calculate weighting factors based on the calculated variances; and
an equalizer configured to transform pixel values of the image using the weighting factors.
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Accused Products
Abstract
The adaptive contrast enhancer uses an adaptive histogram equalization-based approach to improve contrast in a video signal. For each video frame, the histogram of the pixel luminance values is calculated. The calculated histogram is divided into three regions that are equalized independently of the other. The equalized values are averaged with the original pixel values with a weighting factor that depends on the shape of the histogram. The weighting factors can be also chosen differently for the three regions to enhance the darker regions more than the brighter ones. The statistics calculated from one frame are used to enhance the next frame such that frame buffers are not required. Many of the calculations are done in the inactive time between two frames.
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Citations
20 Claims
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1. A contrast enhancement system, comprising:
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a histogram updater configured to; provide a histogram based on an image; determine arithmetic means for at least two regions of the histogram; and calculate variances for each of the determined arithmetic means; a weighting factor calculator configured to calculate weighting factors based on the calculated variances; and an equalizer configured to transform pixel values of the image using the weighting factors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for enhancing contrast of an image, comprising:
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generating a histogram based on an image; determining arithmetic means for at least two regions of the histogram; calculating variances for each of the determined arithmetic means; calculating weighting factors based on the calculated variances; and transforming pixel values of the image using the weighting factors. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A non-transitory computer readable medium encoded with instructions for enhancing contrast of an image, the computer readable medium comprising instructions for:
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generating a histogram based on an image; determining arithmetic means for at least two regions of the histogram; calculating variances for each of the determined arithmetic means; calculating weighting factors based on the calculated variances; and transforming pixel values of the image using the weighting factors. - View Dependent Claims (19, 20)
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Specification