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    COMPRESSION OF BINARY HALFTONES
    21.
    发明专利
    COMPRESSION OF BINARY HALFTONES 未知

    公开(公告)号：CA2008370C

    公开(公告)日：1995-02-07

    申请号：CA2008370

    申请日：1990-01-23

    Applicant: IBM

    Inventor： TOYOKAWA KAZUHARA ,  PENNEBAKER WILLIAM B ,  ANDERSON KAREN L ,  MITCHELL JOAN L

    IPC: G06T9/00 ,  H04N1/41

    Abstract: : A system is described for reformatting halftone data for compression, wherein an original bilevel image is reformatted to produce another bilevel image that allows vertical correlations to be recognized by the compression technique, thus improving compressibility dramatically, with particular suitability for facsimile transmissions. In reformatting it is assumed that a selected halftone frequency H will satisfactorily describe an entire document, and each of successive sets of N consecutive lines are concatenated to form respective single lines. The thus reformatted lines have a clearer halftone periodicity offering greater correlation and permit more efficient coding by well-known standard bilevel compression algorithms (e.g., CCITT G3 (MR) or G4 (MMR)). For an image with unknown pattern frequency, a technique for readily estimating the frequency for use in reformatting the image is described. Y0989-001

    SOFT COPY DISPLAY OF FACSIMILE IMAGES
    22.
    发明专利
    SOFT COPY DISPLAY OF FACSIMILE IMAGES 未知

    公开(公告)号：CA1274025A

    公开(公告)日：1990-09-11

    申请号：CA532513

    申请日：1987-03-19

    Applicant: IBM

    Inventor： PENNEBAKER WILLIAM B ,  MITCHELL JOAN L ,  MINTZER FREDERICK C

    IPC: H04N1/00 ,  G06T3/40 ,  G09G3/00 ,  G09G3/20 ,  G09G5/34 ,  G09G5/36 ,  G09G5/39 ,  G09G5/395 ,  H04N1/387 ,  H04N1/40 ,  G06F15/66

    Abstract: SOFT COPY DISPLAY OF FACSIMILE IMAGES Digital data defining images are stored in a multiplane buffer. The buffer may store plural images by restricting data corresponding to an image or image portion to less than half the bit planes of the buffer. An image is displayed by reading data from the buffer and selectively passing only a portion of the data read to a display. The data defining the images may be converted from facsimile (single bit per pixel) to grey scale format (multiple bits per pel) before being written to the buffer. The conversion relies on a table storing data definitive of the effect, on the image, of a facsimile transition (1/0 or 0/1) as a function of the location or the transition. Conversion from facsimile to grey scale is effected by examining the facsimile data for data transition and summing the effect of each of the transitions to convert a segment of facsimile data to grey scale data. A system is also disclosed for rapidly converting an image in run-end form to a reduced-resolution gray-tone image.

    METHOD FOR ROTATING A BINARY IMAGE
    23.
    发明专利
    METHOD FOR ROTATING A BINARY IMAGE 未知

    公开(公告)号：CA1222081A

    公开(公告)日：1987-05-19

    申请号：CA467899

    申请日：1984-11-15

    Applicant: IBM

    Inventor： ANDERSON KAREN L ,  MINTZER FREDERICK C ,  GOERTZEL GERALD ,  MITCHELL JOAN L

    IPC: G06T3/60 ,  G09G3/00

    Abstract: A method for rotating an image by 90 degrees includes the steps of: storing the image in a raster format arranged in r rows by c columns, image information in each row being stored in a number of bytes, each byte having b bits, there being c/b bytes in each row of the raster format; moving a block of the image into a temporary storage, there being n rows by m columns in the block; separating each image block into groups of bytes of rotatable size; determining for each group if all bits are the same value; rotating each group that does not have all bits the same value; storing each rotated group in an output area of the raster storage; repeating the above steps for all remaining blocks of the image.

    METHOD AND APPARATUS FOR COMPRESSING AND DECOMPRESSING STRINGS OF ELECTRICAL DIGITAL DATA BITS
    24.
    发明专利
    METHOD AND APPARATUS FOR COMPRESSING AND DECOMPRESSING STRINGS OF ELECTRICAL DIGITAL DATA BITS 未知

    公开(公告)号：CA1191957A

    公开(公告)日：1985-08-13

    申请号：CA358588

    申请日：1980-08-19

    Applicant: IBM

    Inventor： MITCHELL JOAN L ,  QUARENDON PETER

    IPC: G06F5/00 ,  G06T9/00 ,  H03M7/30 ,  H04N1/415 ,  H04N7/12 ,  H03M7/36

    Abstract: A compression technique for a character graphics system in which character cell definition bit strings are transmitted from a central processing unit to a display unit. Each cell is divided into a number of slices and each slice into digits. A test is made on whether to compress on a comparison with an all zero slice, the previous slice or the previous slice but one, depending upon the number of digit mismatches that occur when the comparison occurs. Slices are then compressed by comparing each digit with the corresponding digit in the comparison slice and generating a single 0 bit if the digit matches and including a 1 bit and the whole digit if a mismatch occurs. The compression in the central processing unit and the decompression in the display unit is implemented in microcoded routines.

    GRAY SCALE IMAGE DATA COMPRESSION WITH CODE WORDS A FUNCTION OF IMAGE HISTORY
    25.
    发明专利
    GRAY SCALE IMAGE DATA COMPRESSION WITH CODE WORDS A FUNCTION OF IMAGE HISTORY 未知

    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

    IPC: H04N1/411 ,  G06T9/00 ,  H03M7/40 ,  H04N1/41 ,  H04N7/26 ,  H04N7/30 ,  H04N7/32 ,  H04N7/16

    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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