| 摘要 |
A data compression apparatus and a data compression program storage medium are provided to determine a type of compressed data, divide the compressed data into upper data and lower data, and perform a reversible compression process for the upper and lower data, thereby enabling compression of CT(Continuous Tone) data and performing the reversible compression process without deterioration of image quality. A type determining unit determines a type of compressed data. A difference generating unit acquires a difference between neighboring values in the sequence of values composing the compressed data to generate new data compressing apparatus data composed of a sequence of values indicating the difference. An offset unit(520) offsets each value composing the new compressed data as much as a predetermined value. A division unit(530) divides each value of the compressed data, wherein the each value is offset by the offset unit, into an upper bit part and a lower bit part at a predetermined number of division bits smaller than a number of unit bits in order to divide the compressed data into upper data composed of a sequence of upper bit parts of the values and lower data composed of a sequence of lower bit parts of the values. A lower data compressing unit(540) performs a reversible compression process for the lower data divided by the division unit according to the type determined by the type determining unit. An upper data compressing unit(550) performs a reversible compression process for the upper data divided by the division unit.
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