| 摘要 |
An image compression apparatus includes: a line memory unit for holding pixel values for at least one immediately previous line in the lines to be processed of an image to be compressed: a division unit for dividing pixels or the line to be processed into 2 n -pixel blocks; a first estimation, value calculation unit for extrapolation-estimating the 2 n-1 -th pixel and the 2 n -th pixel in the blocks divided by the division unit using, as reference values, the values of pixels immediately above the 2 n-1 -th pixel and the 2 n -th pixel respectively, and obtaining an estimated, value in processing for the first hierarchical level; a second estimation value calculation unit for interpolation-estimating certain pixels using, as reference values, the pixel values of one immediately previous line in the line memory and the estimated, values obtained up to the processing for an immediately previous hierarchical level, and obtaining an estimated value in the processing for the second hierarchical level through the processing for the n-th hierarchical level; and an estimation coding unit for obtaining an estimation error from the estimated value obtained in the processes from the processing for the first hierarchical level to the processing for the n-th hierarchical level, converting the estimation error into a quantization number, converting the quantization number into a variable length, code, and obtaining a compression code. |
