Method of and apparatus for compressing image data

Details Method of and apparatus for compressing image data Method of and apparatus for compressing image data

1989-06-21

1993-02-16

Couso, Jose

Image analysis

Histogram processing

For setting a threshold

382 43, 358133, 358432, 358433, G06K 936

Patent

active

051877554

ABSTRACT:
Image data (f.sub.ij) depicting an image in a pixel block are converted by 2-D Discrete Cosine Transformation into transformation coefficients (F.sub.mn or F.sub.mn *). Only a part of the coefficients are employed to form compressed image data (D.sub.t). The selection of the part of the coefficients is executed using code tables (CT). Several groups of code tables are prepared, and one of those groups is selected in the data compression operation in response to a standard deviation (.sigma.) of the image data in the pixel block. When the compressed image data is restored, identification data specifying the selected group in the previous data compression is stored in the restored image data. Then, in the next data compression of the restored image data, the selected group is again selected as a function of the identification data.

REFERENCES:
patent: 4760461 (1988-07-01), Sato
patent: 4792851 (1988-12-01), Mochizuki
patent: 4910609 (1990-03-01), Nicholas et al.
patent: 4918541 (1990-04-01), Ishida et al.
patent: 4922273 (1990-05-01), Yonekawa et al.
patent: 4947447 (1990-08-01), Miyaoka et al.
IEEE International Conference on Acoustics, Speech and Signal Processing, by Zhang et al., entitled "A New Adaptive Classified Transform Coding Method", 1989, vol. 3, pp. 1835-1837.
The Image Coding publication by Kummerfeldt et al., entitled "Coding Television Signals at 320 and 64 kbit/s", vol. 594, 1985 pp. 119-128.

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