Method for compressing and restoring data of binary image

摘要

A method for compressing and restoring data of a binary image is provided to bind four pixels into one cell for compression, without compressing the image by the pixel, and to compress each cell twice, so as to enhance a compression ratio of the binary image. In a first step to compress S-value, a preprocessing unit(301) performs preprocessing with a rearranged image, to extract S-value of each cell(302). A delay(302) delays the extracted S-value. A probability estimator(304) for S-value estimates the probability for the S-value, and estimates the probability for a current symbol. A first entropy encoder(305) for S-value performs entropy encoding for the estimated probability using arithmetic coding for outputting through a multiplexer(312). In a second step to compress C-value of each cell using the compressed S-value, the image passing the preprocessing unit is stored in an image buffer(306). S-value of a cell to be currently compressed is calculated(307). C-value is extracted from the image buffer(309). A delay(310) delays the C-value. A probability estimator(308) for C-value estimates the probability for the C-value, and estimates the probability for a current symbol. And a second entropy encoder(311) for C-value performs entropy coding for the estimated probability using arithmetic coding for outputting through the multiplexer.