| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for compressing an image with gradation by which image data which is subjected to a pseudo-halftone processing can be efficiently compressed and to provide a method for uncompressing, a compressing device and an uncompressing device. SOLUTION: For compressing an image, an estimated image 42 is generated by reducing an input binary image 36 to an average image 38 by an average calculating unit 37 and by using a halftone screen matrix 40 in combination with the average image 38 by an estimating device 28A. Then an after-image 46 is generated by comparing the estimated image 42 to the input binary image 36 by an exclusive logical addition operator 44. The residual image 46 and the average image 38 are compressed by a compressing unit 27 and are stored or transmitted. For uncompressing the image, after uncompressing the after-image 46 and the average image 38, the average image 38 is zoomed to an image approximately in the size of the input binary image 36. Then an estimated image is formed by a pseudo-halftone processing by using the halftone screen matrix 40 and the image is rebuilt with the estimated image 42 and the after-image 46.
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