A study on the speed of top-down and bottom-up DF-encoding/decoding algorithms for binary pictures

The depth-first picture expression (DF-Expression) is an effective data compression technique for binary images. When one applies it to real equipment, one needs a practical encoding/decoding scheme which should be fast and simple in the operation. The authors study two types of coding algorithm, one is the top-down and the other is the bottom-up methods. These algorithms are put into two C programs to compare the speed. The authors have designed an encoding/decoding hardware device, and built it on a breadboard which is linked to a workstaton. The hardware encoder/decoder can achieve a 50-100 times faster operation than the C programs run on a 4 MIPS workstation