Modified Compression Techniques Based on Optimality of LZW Code (MOLZW)
Utpal Nandi, Jyotsna Kumar Mandal · Procedia Technology · 2013
A lossless dictionary-based data compression technique has been proposed in this paper which is the modified form of compression technique based on optimality of LZW code (OLZW). The encoding process of proposed technique is almost similar with OLZW. Additionally a checking is performed to determine the dictionary is full or not before insertion of new entry into the dictionary. When the dictionary gets full, the least recently used dictionary phrase is deleted. A variant of the same is also proposed where no phrases of dictionary are deleted. But, phrases added to the dictionary are all the string formed by concatenation of previous match and prefix of current match including current match itself. Another technique is proposed which combines both the above proposed techniques. Comparisons of compression ratios are made among LZW, OLZW and proposed techniques which shows that the proposed techniques work well not only for small size files but also for large size files.