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公开(公告)号：CA1213033A
公开(公告)日：1986-10-21
申请号：CA455137
申请日：1984-05-25
Applicant: IBM
Inventor： ANASTASSIOU DIMITRIS
Abstract: Graphics images are generally considered to be those images comprised of text and/or drawings. Data compression of graphics images is desired whenever a fast image transmission speed is desired in a limited band width channel. It is also used for storage of a large number of images in a limited capacity storage system. A high compression ratio is achieved by thresholding the graphics image to a bilevel black-white image at one bit per pixel and then employing a second data compression on the black-white image. At low resolution, bilevel images hate poor quality at edges and a quality improvement is needed. The data compression apparatus and method disclosed separates the graphics image into at least first and second bit planes, identifies edge pixels from the first bit plane indicating a black/white change, locates the edge pixels and generates at least a single bit for each edge pixel indicating whether the edge pixel has a maximum intensity value such as black or white or an intermediate gray intensity value. Intermediate values are not allowed except at edge pixels which enhances both quality and compressibility of the resulting graphics image.
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公开(公告)号：CA1196091A
公开(公告)日：1985-10-29
申请号：CA438410
申请日：1983-10-05
Applicant: IBM
Inventor： ANASTASSIOU DIMITRIS , PENNEBAKER WILLIAM B
Abstract: NONLINEAR FILTERING OF GRAY SCALE IMAGES Apparatus and method are described for filtering noise from digital video images including means for determining first difference values between intensity values of current pel and one or more preceding pels, means for determining second difference values between intensity values of the current pel and one or more succeeding pels, means for limiting any of the first and second difference values that exceed a predetermined limit value, and means for generating a filtered value for the current pel by adding the intensity value of the pel to a scale summation of the limited first and second difference values.
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公开(公告)号：CA1283477C
公开(公告)日：1991-04-23
申请号：CA498545
申请日：1985-12-23
Applicant: IBM
Inventor： ANASTASSIOU DIMITRIS , PENNEBAKER WILLIAM B
IPC: H04N1/40
Abstract: YO9-82-O4OX CORRECTION OF SHADING EFFECTS IN VIDEO IMAGES Video images are corrected for shading effects by generating a histogram of picture element (pel) gray scale intensity values and calculating the median and the black and white extremes thereof. A range of permitted background gray scale values is empirically selected. A background image is then created by sampling the intensity values of the original image pels and using a look-up table to remap the image. In one embodiment, pel intensity values are compared with the median value and only corrections lying within the range are carried out. A duplicate image is created from the remapped image and the intensity values of a number of pels in a predetermined region about a first pel in this image are sampled and the value of the corresponding pel in the background image is changed to the largest value among those of the first pel and the sampled pels. This is continued using a look-up table with a 7 bit output until all of the pels in the background image have been changed accordingly. The duplicate image is then changed to conform to the changed background image and the sampling procedure is carried out over a larger surrounding region.
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Patent Agency Ranking
公开(公告)号：DE3381868D1
公开(公告)日：1990-10-11
申请号：DE3381868
申请日：1983-11-22
Applicant: IBM
Inventor： ANASTASSIOU DIMITRIS , PENNEBAKER WILLIAM BOONE
Abstract: Nonlinear shading correction of an image to improve readability and data compression is effected by means for generating a histogram of distribution of gray scale intensity levels, means for calculating from the histogram first, second and third gray scale intensity values, means for determining image polarity, means for determining an acceptable range of background gray scale variation, means for sampling gray scale intensity values in a region around a current pel, means for calculating a correction value for the current pel by comparing the gray scale value of the current pel with the range of background gray scale variation, means for setting the correction value to a predetermined constant if the gray scale value of the current pel is outside the range of a acceptable background variation, and means for correcting the current pel gray scale value by subtracting therefrom the correction value to achieve a shading corrected value for the current pel.
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公开(公告)号：DE3377449D1
公开(公告)日：1988-08-25
申请号：DE3377449
申请日：1983-11-22
Applicant: IBM
Inventor： ANASTASSIOU DIMITRIS , PENNEBAKER WILLIAM BOONE
Abstract: Filtering noise from digital video images is achieved by means for determining first difference values between intensity values of current pel and one or more preceding pels, means for determining second difference values between intensity values of the current pel and one or more succeeding pels, means for limiting any of the first and second difference values that exceed a predetermined limit value, and means for generating a filtered value for the current pel by adding the intensity value of the pel to a scale summation of the limited first and second difference values.
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公开(公告)号：CA1181862A
公开(公告)日：1985-01-29
申请号：CA399059
申请日：1982-03-23
Applicant: IBM
Inventor： ANASTASSIOU DIMITRIS , MITCHELL JOAN L
Abstract: GRAY SCALE IMAGE DATA COMPRESSION WITH CODE WORDS A FUNCTION OF IMAGE HISTORY The present invention relates to a method and apparatus for compacting gray-scale image data which maintains extremely good picture quality and can result in typical images in a compression ratio of 5 to 1 and even better if a final step of arithmetic coding is used. The method is a special application of adaptive differential pulse code modulation (DPCM) which utilizes a prediction of smoothness surrounding a current pel to determine variable length codes to convey the quantized error. Thus, a continuously adaptive variable length code is produced which may be accurately decoded without using any further marker (code indicator) bits. For each pel an "error bit" is generated to indicate to the decoder if the predicted quantization range is adequate. These error bits can be further significantly compressed. This method permits the use of a "zero bit" per pel mode for the data transmission (1 "error bit" per pel actually transmitted) and provides for the automatic detection of the particular variable length compression code utilized for transmitting the quantized error (Ey) for a particular pel. Utilizing the concepts of the present invention the inventors have obtained compression rates of approximately 1.5 bits per pel that produce a gray scale image at the decoding end of such a data transmission or storage system which has excellent quality (equal to 5 bit DPCM). By adding the concept of arithmetic coding to the previously set forth method, due to the nature of the statistical distribution of said special purpose error bit patterns, a compressed data set of less than 1 bit per pel has been achieved. This was produced from an original 8 bit per pel gray scale image.
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公开(公告)号：DE3478379D1
公开(公告)日：1989-06-29
申请号：DE3478379
申请日：1984-06-08
Applicant: IBM
Inventor： ANASTASSIOU DIMITRIS
Abstract: A first bit plane (bit array) is generated of the graphic image, and then, by comparison/logic circuitry, a second bit plane is generated which identifies only pixels of the graphics image representing edges e.g. of characters or lines in the image. The data stream representing the image from the first bit plane is supplemented by edge bits from the second bit plane.
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公开(公告)号：DE3265983D1
公开(公告)日：1985-10-10
申请号：DE3265983
申请日：1982-04-21
Applicant: IBM
Inventor： ANASTASSIOU DIMITRIS , MITCHELL JOAN LAVERNE
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