IMAGE DATA COMPRESSION APPARATUS AND DECODING APPARATUS

An image data compression apparatus includes: a filter coefficient calculation unit to perform a filter process to separate pixels extracted in accordance with a one-dimensional subband coding into low- and high-frequency components, and to calculate coefficient values of respective filter coefficients; prediction units to perform different predictions respectively for the calculated coefficient values; a predicted coefficient value calculation unit to calculate predicted coefficient values to be used for posterior predictions by calculating each from at least one of predicted values and from corresponding at least one of the calculated coefficient values; a memory unit to hold the predicted coefficient values calculated by the predicted coefficient value calculation unit; and a compression coding unit to calculate a difference between each predicted value and corresponding each coefficient value, and to perform coding after quantizing the difference, or to perform coding on the basis of the difference.