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EP0809209A2
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EP
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Image enhancing method using lowpass filtering and histogram equalization and a device therefor
Assignee: Samsung Electronics Co Ltd
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Filing: 1997-05-14
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Granted: —
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Expires: 2017-05-14
Abstract
Abstract In an image enhancing method, an input image signal is lowpass filtered and then histogram equalized to become a contrast-enhanced signal. Then, the lowpass filtered signal is subtracted from the input image signal. Afterwards, the subtracted value is added to the contrast enhanced signal, and the added result is output as an image enhanced output signal. Thus, the contrast of a given image signal is improved without an increase in background noise. <IMAGE>
Inventors
- 👤 Yeong-Taeg Kim
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 10:27
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/90; G06T5/92; H; H04; H04N; H04N5/00; H04N5/14; H04N5/20; G06T5/40
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
77 words
An image enhancing method by histogram-equalizing an image signal represented by a predetermined number of gray levels, comprising the steps of: (a) lowpass filtering an input image signal to output a lowpass filtered signal; (b) histogram equalizing the lowpass filtered signal to output a contrast-enhanced signal; (c) subtracting the lowpass filtered signal from the input image signal; and (d) outputting a signal produced by adding the subtracted value in said step (c) to the contrast enhanced signal.
Claim 2
Dependent Claim
66 words
An image enhancing method as claimed in claim 1, wherein said step (b) comprises the steps of: calculating a probability density function which represents a gray level distribution in the lowpass filtered signal by a picture unit; calculating a cumulative density function on the basis of the probability density function; and mapping the lowpass filtered signal into a gray level according to the cumulative density function.
Claim 3
Dependent Claim
38 words
An image enhancing method as claimed in claim 1 or 2, wherein the difference between the output signal and the contrast enhanced signal is the same as that between the input image signal and the lowpass filtered signal.
Claim 4
Dependent Claim
93 words
An image enhancing device by histogram equalizing an image signal represented by a predetermined number of gray levels, comprising: lowpass filtering means (100) for lowpass filtering an input image signal and outputting the lowpass filtered signal; histogram equalizing means (200) for histogram equalizing the lowpass filtered signal and outputting a contrast enhanced signal; detecting means (300) for detecting the difference between the input signal and the lowpass filtered signal; and outputting means (400) for adding the detected difference value to the contrast enhanced signal to output the added result as an output signal.
Claim 5
Dependent Claim
86 words
An image enhancing device as claimed in claim 4, wherein said histogram equalizing means (200) comprises: first calculating means (210) for receiving the lowpass filtered signal and calculating a probability density function which represents a gray level distribution in the lowpass filtered signal by a picture unit; second calculating means (220) for calculating a cumulative density function on the basis of the probability distribution function; and mapping means (240) for mapping the lowpass filtered signal into a gray level according to the cumulative density function value.
Claim 6
Dependent Claim
44 words
An image enhancing device as claimed in claim 5, further comprising a picture memory (230) for delaying the lowpass filtered signal by one frame to output a signal in the same frame as the cumulative density function value output by said second calculating means.
Claim 7
Dependent Claim
56 words
An image enhancing device as claimed in claim 5, further comprising a buffer (230) for storing the cumulative density function values calculated by said second calculating means by a picture unit, updating the stored values in response to a synchronization signal, and outputting a cumulative density function value stored one frame before to said mapping means.
References Cited (Backward Citations)
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