EP0188193A2
Expired / Lapsed
EP
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Method and apparatus for processing image data
Assignee: International Business Machines Corp
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Filing: 1986-01-02
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Granted: —
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Expires: 2006-01-02
Abstract
Abstract A method and apparatus for processing images using gray scale techniques includes means (40) for obtaining a histogram of levels in an image; means (42) for analyzing said histogram to identify one or more ranges of background in said image; means (44, 48, 52) for converting each of said ranges of background to a constant value to achieve flat backgrounds in said image; means for generating a dynamic range expansion table for each image; means for correcting said image data for dynamic range compression due to coring during processing of said image data by reference to said dynamic range expansion table. The process may also include means for encoding (54) said processed image using gray scale encoding techniques, means (46) for filtering all nonbackground pixels in said image, means for generating for said image a shading correction for each pixel in said image; means for correcting each pixel for shading employing said shading correction generated for each pixel, means for determining if said image is a graphics image; means for generating a dynamic range expansion table for each graphics image; means for correcting said image data for dynamic range compression by reference to said dynamic range expansion table, means for creating a second table of values from parameters contained in said encoded image data; and means for translating decoded image pixel values by reference to said second table to correct for quantization noise.
Inventors
- 👤 William Boone Pennebaker
- 👤 Joan La Verne Mitchell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 00:34
CPC Classifications
G; G06; G06T; G06T5/00; G06T5/90; G06T5/92; G06T5/40; H; H04; H04N; H04N1/00; H04N1/40; H04N1/401; H04N1/407; H04N1/4072; H04N1/4074
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
58 words
A method for processing image data, characterized by the steps of: obtaining a histogram of intensity levels in an image; analyzing the histogram to identify one or more ranges of background in the image; converting each of the ranges of background to a single value to achieve a constant intensity for each of the ranges in said image.
Claim 2
Independent Claim
58 words
A method for processing image data, characterized by the steps of: obtaining a histogram of intensity levels in an image; analyzing the histogram to identify one or more ranges of background in the image; converting each of the ranges of background to a single value to achieve a constant intensity for each of the ranges in said image.
Claim 3
Dependent Claim
24 words
A method for processing image data according to claim 1 further comprising the step of: encoding the processed image using gray scale encoding techniques.
Claim 4
Dependent Claim
22 words
A method for processing image data according to claim 1 further comprising the step of: filtering all nonbackground pixels in the image.
Claim 5
Dependent Claim
40 words
A method for processing image data according to claim 1 wherein said step of analyzing the histogram further comprises the steps of: determining edge intensity values for each background range and determining a peak intensity value for each background range.
Claim 6
Dependent Claim
41 words
A method for processing image data according to claim 1 further comprising the steps of: generating for the image a shading correction for each pixel in the image; correcting each pixel for shading employing the shading correction generated for each pixel.
Claim 7
Dependent Claim
105 words
A method for processing image data according to claim 5 wherein the step of generating a shading correction further comprises the steps of: testing value of predetermined pixels in a block to determine if the value falls within a background range; assigning a value equal to an average value of a previous block to those predetermined pixels in said block having a value outside the background range; averaging values of pixels having values within the background range with assigned values of the pixels to obtain a block average value; offsetting the average intensity values by the peak background value to obtain signed pixel shading corrections.
Claim 8
Dependent Claim
63 words
7 . A method for processing image data according to claim 5 or 6 wherein the step of generating a shading correction further comprises the step of: generating a previous block average value for a first block of pixels by assigning a value of a closest background edge value to those predetermined pixels within the first block which fall outside the background range.
Claim 9
Dependent Claim
26 words
A Method for processing image data according to claim 6 further comprising the step of: interpolating a shading correction for each pixel from said block averages.
Claim 10
Dependent Claim
49 words
A method for processing image data according to claim 1 further comprising the steps of: determining if the image is a graphics image; generating a dynamic range expansion table for each graphics image; correcting the image data for dynamic range compression by reference to said dynamic range expansion table.
Claim 11
Independent Claim
48 words
A method for decoding encoded image data characterized by the steps of: generating a dynamic range expansion table for each image; decoding the image data using an appropriate gray scale decoding algorithm; correcting the image data for dynamic range compression by reference to said dynamic range expansion table.
Claim 12
Independent Claim
48 words
A method for decoding encoded image data characterized by the steps of: generating a dynamic range expansion table for each image; decoding the image data using an appropriate gray scale decoding algorithm; correcting the image data for dynamic range compression by reference to said dynamic range expansion table.
Claim 13
Dependent Claim
46 words
A Method for decoding encoded image data according to claim 10 further comprising the steps of: creating a second table of values from parameters contained in said encoded image data; translating decoded image pixel values by reference to the second table to correct for quantization noise.
Claim 14
Dependent Claim
65 words
Apparatus for processing image data, characterized by: means (40) for obtaining a histogram of intensity levels in an image; means (42) for analysing the histogram to identify one or more ranges of background in said image; means (44, 48, 52) for converting each of said ranges of background to a single value to achieve a constant intensity for each of said ranges in said image.
Claim 15
Dependent Claim
65 words
Apparatus for processing image data, characterized by: means (40) for obtaining a histogram of intensity levels in an image; means (42) for analysing the histogram to identify one or more ranges of background in said image; means (44, 48, 52) for converting each of said ranges of background to a single value to achieve a constant intensity for each of said ranges in said image.
Claim 16
Dependent Claim
33 words
Apparatus for processing image data according to claim 14 further comprising: means (46) for filtering all nonbackground pixels in the image; means for (54) encoding the processed image using gray scale encoding techniques.
Claim 17
Dependent Claim
40 words
Apparatus for processing image data according to claim 12 wherein said means for analyzing the histogram further comprises means for determining edge intensity values for each background range and means for determining a peak intensity value for each background range.
Claim 18
Dependent Claim
53 words
Apparatus for decoding encoded image data characterized by means (66) for generating a dynamic range expansion table for each image; means (68) for decoding said image data using an appropriate gray scale decoding algorithm; and means for correcting said image data for dynamic range compression by reference to said dynamic range expansion table.
Claim 19
Dependent Claim
53 words
Apparatus for decoding encoded image data characterized by means (66) for generating a dynamic range expansion table for each image; means (68) for decoding said image data using an appropriate gray scale decoding algorithm; and means for correcting said image data for dynamic range compression by reference to said dynamic range expansion table.
Claim 20
Dependent Claim
47 words
Apparatus for decoding encoded image data according to claim 15 further comprising: means for creating a second table of values from parameters contained in said encoded image data; and means for translating decoded image pixel values by reference to the second table to correct for quantization noise.
References Cited (Backward Citations)
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