Patent US6646611B2 successfully refreshed from Google Patents.
Patent US6199063B1 successfully refreshed from Google Patents.
EP0383269A2
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Regionally adaptive imaging techniques
Assignee: Adler Research Associates
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Filing: 1990-02-13
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Granted: —
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Expires: 2010-02-13
Abstract
Abstract A first regionally adaptive imaging technique, for enhancing the contrast of a digital image, employs an adaptive histogram equalization technique in which the histogram associated with a contextual region is low pass filtered, prior to developing the mapping function, of original pixel intensity to adjusted pixel intensity, from the histogram. A second technique for enhancing the contrast of images within a smooth background employs a regionally adaptive filter in which the intensity of selected pixels are adjusted in accordance with a transformation which is a function of the mode of pixel intensities, and deviations from the mode of pixel intensities, within a contextual region corresponding to the selected pixel. <IMAGE> <IMAGE>
Inventors
- 👤 Dimitris Manolakis
- 👤 Vassilios V. Digalakis
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 22:35
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/90; G06T5/94; G06T5/40; G06T2207/00; G06T2207/20; G06T2207/20004; G06T2207/20012
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
155 words
A method for enhancing the contrast of an image formed of a plurality of pixels, each having an intensity level and a location within said image, comprising: storing intensity levels of said plurality of pixels in a memory device; selecting a plurality of pixels, each of said selected pixels associated with a contextual region of said image; determining a histogram of frequency of occurrence versus pixel intensity for each of said contextual regions; low pass filtering each of said histograms to produce a plurality of filtered histograms; determining a mapping function of the original pixel intensity to adjusted pixel intensity for each of said filtered histograms; adjusting the intensity of each of the selected pixels in accordance with the mapping function associated with each selected pixel, to produce a plurality of adjusted pixel intensities; and replacing, in said memory device, the intensity level of each of said selected pixels with its associated adjusted pixel intensity.
Claim 2
Independent Claim
155 words
A method for enhancing the contrast of an image formed of a plurality of pixels, each having an intensity level and a location within said image, comprising: storing intensity levels of said plurality of pixels in a memory device; selecting a plurality of pixels, each of said selected pixels associated with a contextual region of said image; determining a histogram of frequency of occurrence versus pixel intensity for each of said contextual regions; low pass filtering each of said histograms to produce a plurality of filtered histograms; determining a mapping function of the original pixel intensity to adjusted pixel intensity for each of said filtered histograms; adjusting the intensity of each of the selected pixels in accordance with the mapping function associated with each selected pixel, to produce a plurality of adjusted pixel intensities; and replacing, in said memory device, the intensity level of each of said selected pixels with its associated adjusted pixel intensity.
Claim 3
Dependent Claim
40 words
The method of claim 1, further comprising the steps of monitoring said image after replacing said selected pixels with said adjusted pixels; and interactively changing one or more low pass filter parameters employed during said step of low pass filtering.
Claim 4
Dependent Claim
30 words
The method of claim 1 wherein said step of low pass filtering includes the step of determining a running average of frequency of occurrence as a function of pixel intensity.
Claim 5
Independent Claim
187 words
An apparatus for enhancing the contrast of an image (10) formed of a plurality of pixels (12, 14) each having an intensity level and a location within said image, comprising a computer (26) having: a memory device (32) for storing intensity levels of said pixels (12, 14) which form said image (10), and a processor (34, 36, 38) for (i) selecting a plurality of said pixels (12, 14), each of said selected pixels associated with a contextual region (16, 18) of said image (10), (ii) determining a histogram of frequency of occurrence versus pixel intensity for each of said contextual regions, (iii) low pass filtering each of said histograms to produce a plurality of filtered histograms, (iv) determining a mapping function of original pixel intensity to adjusted pixel intensity for each of said filtered histograms, (v) adjusting the intensity of each of the selected pixels in accordance with the mapping function associated with each selected pixel, to produce a plurality of adjusted pixel intensities, and (vi) replacing, in said memory device (32), the intensity level of each of said selected pixels with its associated adjusted pixel intensity.
Claim 6
Independent Claim
187 words
An apparatus for enhancing the contrast of an image (10) formed of a plurality of pixels (12, 14) each having an intensity level and a location within said image, comprising a computer (26) having: a memory device (32) for storing intensity levels of said pixels (12, 14) which form said image (10), and a processor (34, 36, 38) for (i) selecting a plurality of said pixels (12, 14), each of said selected pixels associated with a contextual region (16, 18) of said image (10), (ii) determining a histogram of frequency of occurrence versus pixel intensity for each of said contextual regions, (iii) low pass filtering each of said histograms to produce a plurality of filtered histograms, (iv) determining a mapping function of original pixel intensity to adjusted pixel intensity for each of said filtered histograms, (v) adjusting the intensity of each of the selected pixels in accordance with the mapping function associated with each selected pixel, to produce a plurality of adjusted pixel intensities, and (vi) replacing, in said memory device (32), the intensity level of each of said selected pixels with its associated adjusted pixel intensity.
Claim 7
Dependent Claim
46 words
The apparatus of claim 4 further comprising a monitor (30) connected to said computer (26) for displaying said image (10), and a manual input device (28) for changing parameters of said processor (34, 36, 38) to effect changes in said low pass filtering of said histograms.
Claim 8
Dependent Claim
34 words
The apparatus of claim 4, wherein said processor (34, 36, 38) determines a running average of frequency of occurrence, as a function of pixel intensity, to provide said low pass filtering of said histogram.
Claim 9
Independent Claim
159 words
A method for enhancing the contrast of an image formed of a plurality of pixels each having an intensity level and a location within said image, comprising: storing intensity levels of said plurality of pixels in a memory device; selecting a plurality of said pixels, each of said selected pixels associated with a contextual region of said image; determining the mode of pixel intensities over each of said contextual regions; determining the deviation of pixel intensities, in each contextual region, from the mode in the respective contextual region; adjusting the intensity of each selected pixel in accordance with a transformation which is a function of the mode of pixel intensities and deviation from the mode of pixel intensities, in the contextual region corresponding to the selected pixel, to produce an adjusted intensity for each of said selected pixels; and replacing, in said memory device, the intensity level of each of said selected pixels with its associated adjusted pixel intensity.
Claim 10
Independent Claim
159 words
A method for enhancing the contrast of an image formed of a plurality of pixels each having an intensity level and a location within said image, comprising: storing intensity levels of said plurality of pixels in a memory device; selecting a plurality of said pixels, each of said selected pixels associated with a contextual region of said image; determining the mode of pixel intensities over each of said contextual regions; determining the deviation of pixel intensities, in each contextual region, from the mode in the respective contextual region; adjusting the intensity of each selected pixel in accordance with a transformation which is a function of the mode of pixel intensities and deviation from the mode of pixel intensities, in the contextual region corresponding to the selected pixel, to produce an adjusted intensity for each of said selected pixels; and replacing, in said memory device, the intensity level of each of said selected pixels with its associated adjusted pixel intensity.
Claim 11
Dependent Claim
129 words
The method of claim 7, wherein said step of determining the deviation of pixel intensities includes the steps of determining a first deviation of pixel intensities from the mode, for pixels having an intensity lower than the mode, and determining a second deviation of pixel intensities from the mode, for pixels having an intensity greater than the mode, and wherein said step of adjusting the intensity of each selected pixel, includes the steps of adjusting the intensities of said selected pixels having intensities less than the mode in accordance with a first transformation which is a function of the first deviation; and adjusting the intensities of said selected pixels having intensities greater than the mode in accordance with a second transformation which is a function of the second deviation.
Claim 12
Independent Claim
186 words
An apparatus for enhancing the contrast of an image (10) formed of a plurality of pixels (12, 14), each having an intensity level and a location within said image, comprising a computer (44) having: a memory device (32) for storing intensity levels of said pixels (12, 14) which form said image (10), and a processor (46, 48, 50) for (i) selecting a plurality of said pixels (12, 14) each associated with a contextual region (16, 18) of said image (10), (ii) determining the mode of pixel intensities over each of said contextual regions, (iii) determining the deviation of pixel intensities, in each contextual region, from the mode in the respective contextual region, (iv) adjusting the intensity of each selected pixel in accordance with a transformation which is a function of the mode of pixel intensities, and deviation from the mode of pixel intensities, in the contextual region corresponding to the selected pixel, to produce an adjusted intensity for each of said selected pixels, and (v) replacing, in said memory device (32), the intensity level of each of said selected pixels with its associated adjusted pixel intensity.
Claim 13
Independent Claim
186 words
An apparatus for enhancing the contrast of an image (10) formed of a plurality of pixels (12, 14), each having an intensity level and a location within said image, comprising a computer (44) having: a memory device (32) for storing intensity levels of said pixels (12, 14) which form said image (10), and a processor (46, 48, 50) for (i) selecting a plurality of said pixels (12, 14) each associated with a contextual region (16, 18) of said image (10), (ii) determining the mode of pixel intensities over each of said contextual regions, (iii) determining the deviation of pixel intensities, in each contextual region, from the mode in the respective contextual region, (iv) adjusting the intensity of each selected pixel in accordance with a transformation which is a function of the mode of pixel intensities, and deviation from the mode of pixel intensities, in the contextual region corresponding to the selected pixel, to produce an adjusted intensity for each of said selected pixels, and (v) replacing, in said memory device (32), the intensity level of each of said selected pixels with its associated adjusted pixel intensity.
Claim 14
Dependent Claim
91 words
The method of claim 7 or the apparatus of claim 9, wherein said transformation is in accordance with the relationship: where f i (x,y) is the original intensity, f o (x,y) is the adjusted intensity, f peak (x,y) is the intensity of the mode within said contextual region, µ D is the desired mode within said contextual region, σ D is the desired deviation from the mode within said contextual region, σ ′ x ,y is the deviation from the mode within said contextual region, and A and α are constants.
Claim 15
Dependent Claim
103 words
The apparatus of claim 9, wherein said processor (46, 48, 50) (a) determines a first deviation from the mode, for pixels having an intensity lower than the mode, (b) determines a second deviation of pixel intensities from the mode, for pixel intensities greater than the mode, (c) adjsuts the intensities of said selected pixels having intensities less than the mode in accordance with a first transformation which is a function of the first deviation, and (d) adjusts the intensities of said selected pixels having intensities greater than the mode, in accordance with a second transformation which is a function of the second deviation.
Claim 16
Dependent Claim
105 words
The method of claim 8 or the apparatus of claim 11, wherein said first transformation is in accordance with the relationship: and said second transformation is in accordance with the relationship: where f i (x,y) is the original intensity, f o (x,y) is the adjusted intensity, f peak (x,y) is the intensity of the mode within said contextual region, µ D is the desired mode within said contextual region, σ D is the desired deviation from the mode within said contextual region, σ L is the first deviation and σ H is the second deviation within said contextual region, and A and α are constants.
Claim 17
Independent Claim
36 words
The method of any one of claims 1 to 3, 7, 8, 10 and 12 or apparatus of any one of claims 4 to 6 and 9 to 12, wherein said image is a radiological image.
References Cited (Backward Citations)
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