which a system bandwidth can accommodate for example four least significant bits lsb of the pixel brightness for each color are truncated as shown in second column before truncation and the third column after truncation of table iii the average pixel size of the current block n 1 after truncation coding becomes 12 bits pixel this average pixel size i e 12 is averaged with the average pixel size i e 9 of preceding blocks up to the block n and the average pixel size of preceding blocks up to the block n 1 is updated as 10 5 9 12 2 bits pixel table iii before after original truncation truncation in decimal in binary in binary 20 00010100 0001 128 10000000 1000 200 11001000 1100 255 11111111 1111 for the block n 1 the truncated results in table iii are allowed to pass step 15 by the compression controller 24 as output in lieu of the results of entropy coding in table ii fig2 a illustrates a flow diagram of associated image decompression method according to the embodiment of the present invention and fig2 b illustrates a block diagram of associated image decompression apparatus according to the embodiment at the outset of the decompression a decompression controller 44 determines whether the pixels temporarily stored in a buffer 42 have ever been truncated step 30 the determination of truncation is usually performed by but not limited to examining header transported from a compressor encoder if the determination is negative the pixels are subjected to a decompression or decompressions step 31 of a decompressor 40 that are the inverse operation s of the compressor 20 on the other hand if the determination of step 30 is affirmative the pixels are subjected to reconstruction step 32 by.