How many bits reduce algorithum are there I need algorithm t

How many bits reduce algorithum are there? I need algorithm that help me to reduce 8-bits into 4 bits and this method is apply in encryption and decryption

Solution

There are many bit compression algorityms and are broadly classified as loseless and lossy compressions. Lossless compression reduces bits removing statistical redundancy and no information is lost in lossless compression. Lossy compression reduces bits by removing unnecessary or less important information. In lossless compression  Lempel Ziv (LZ) compression techniques are among the most popular algorithms , similarly Deflate is another technique. On the other hand lossy compression is used in image compressions like Jpeg etc. One of the important lossless compression is a Huffman code which is a type of optimal prefix code that is commonly used for lossless data compression.