| 摘要 |
Compressed image data from a code memory is separated into quantization step values, code table information and variable-length codes. The variable-length codes are each decoded into a run length, a size and an additional bit string and written into a size memory. A size conversion section converts the run length, the size and the additional bit string from the size memory based on a frequency region and a size conversion amount set in a size conversion table. A variable-length code is assigned to each converted run length/size combination, and an additional bit string is attached thereto, thereby producing a variable-length code. The variable-length codes, the quantization step values and the code table information are multiplexed together to produce compressed image data.
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