ENCODER

摘要

PURPOSE:To make the border of blocks inconspicuous and to obtain high encoding efficiency by forecasting a level by performing approximation in a block to a curved surface or plane and representing a forecasted difference in many gradations. CONSTITUTION:A buffer memory 12 devices an image into blocks consisting of plural picture elements and determines a reference value for each block and a forecasted value arithmetic circuit 13 forecast the gradation level of each picture element in each block. Then a forecasted difference arithmetic means 14 finds forecasted differences between the gradation levels of respective image elements and a forecasted value and a maximum forecasted difference calculating means 15 decides the largest absolute value among those forecasted differences. Then a representative difference for approximating this maximum forecasted difference is determined and resolution components showing which representative difference value the forecasted differences are approximated are specified by image elements. Consequently, the block border is not conspicuous and the high encoding efficiency is obtained.