Method for estimating and adjusting digital image contrast
First Claim
1. A method of estimating the scene contrast from a digital image, the method comprising the steps of:
- a) determining a Laplacian value for value for each pixel of the digital image;
b) forming a Laplacian histogram distribution based on the Laplacian values;
c) determining, from the Laplacian histogram, first and second thresholds which eliminate substantially uniform areas or substantially textured portion of the digital image;
d) selecting pixels which are based on the first and second thresholds from the digital image;
e) forming an intensity histogram from the selected pixels;
f) computing a standard deviation of the intensity histogram; and
g) estimating contrast of the digital image by comparing the computed standard deviation with a predetermined contrast for determining contrast of the input image in relationship with the predetermined contrast.
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Abstract
A method of estimating the scene contrast from a digital image, the method comprises the steps of: forming a Laplacian histogram distribution; determining, from the Laplacian histogram, first and second thresholds which eliminate substantially uniform areas or a substantially textured portion of the digital image; selecting pixels which are based on the first and second thresholds from the digital image; forming a histogram from the sampled pixels; computing a standard deviation of the sampled histogram; and estimating contrast of the digital image by comparing the computed standard deviation with a predetermined contrast for determining contrast of the input image in relationship with the predetermined contrast.
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Citations
43 Claims
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1. A method of estimating the scene contrast from a digital image, the method comprising the steps of:
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a) determining a Laplacian value for value for each pixel of the digital image; b) forming a Laplacian histogram distribution based on the Laplacian values; c) determining, from the Laplacian histogram, first and second thresholds which eliminate substantially uniform areas or substantially textured portion of the digital image; d) selecting pixels which are based on the first and second thresholds from the digital image; e) forming an intensity histogram from the selected pixels; f) computing a standard deviation of the intensity histogram; and g) estimating contrast of the digital image by comparing the computed standard deviation with a predetermined contrast for determining contrast of the input image in relationship with the predetermined contrast. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of estimating the scene contrast from a digital image, the method comprising the steps of:
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a) determining a Laplacian value for each pixel of the digital image; b) forming a Laplacian histogram distribution based on the Laplacian values; c) determining, from the Laplacian histogram, first and second thresholds; d) selecting pixels which are based on the first and second thresholds from the digital image; e) forming an intensity histogram from the selected pixels; f) forming a target histogram from the intensity histogram by convolving the intensity histogram with a pre-defined function; and g) constructing a tone scale curve by transforming the intensity histogram to the target histogram. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A computer program product for excluding pixels from a uniform portion or a texture portion of a digital image, comprising a computer readable storage medium having a computer program stored thereon for performing the steps of:
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a) determining a Laplacian value for each pixel of the digital image; b) forming a Laplacian histogram distribution based on the Laplacian values; c) determining, from the Laplacian histogram, first and second thresholds which eliminate substantially the uniform portion or substantially the textured portion of the digital image; and d) selecting pixels which are based on the first and second thresholds from the digital image.
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22. A method for excluding pixels from a uniform portion or a texture portion of a digital image, comprising the steps of:
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a) determining a Laplacian value for each pixel of the digital image; b) forming a Laplacian histogram distribution based on the Laplacian values; c) determining, from the Laplacian histogram, first and second thresholds which eliminate substantially the uniform portion or substantially the textured portion of the digital image; and d) selecting pixels which are based on the first and second thresholds from the digital image. - View Dependent Claims (23)
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24. A computer program product for estimating the scene contrast from a digital image, comprising:
- a computer readable storage medium having a computer program stored thereon for performing the steps of;
a) determining a Laplacian value for each pixel of the digital image; b) forming a Laplacian histogram distribution based on the Laplacian values; c) determining, from the Laplacian histogram, first and second thresholds which eliminate substantially uniform areas or substantially textured portion of the digital image; d) selecting pixels which are based on the first and second thresholds from the digital image; e) forming an intensity histogram from the selected pixels; f) computing a standard deviation of the intensity histogram; and g) estimating contrast of the digital image by comparing the computed standard deviation with a predetermined contrast for determining contrast of the input image in relationship with the predetermined contrast. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
- a computer readable storage medium having a computer program stored thereon for performing the steps of;
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36. A computer program product for estimating the scene contrast from a digital image, comprising:
- a computer readable storage medium having a computer program stored thereon for performing the steps of;
a) determining a Laplacian value for each pixel of the digital image; b) forming a Laplacian histogram distribution based on the Laplacian values; c) determining, from the Laplacian histogram, first and second thresholds; d) selecting pixels which are based on the first and second thresholds from the digital image; e) forming an intensity histogram from the selected pixels; f) forming a target histogram from the intensity histogram by convolving the intensity histogram with a predefined function; and g) constructing a tone scale curve by transforming the intensity histogram to the target histogram. - View Dependent Claims (37, 38, 39, 40, 41, 42, 43)
- a computer readable storage medium having a computer program stored thereon for performing the steps of;
Specification