JPEG: Entropy Coding
Data, which result from the preceding steps, are provided with a different quantity of redundancy, which does not supply any contribution for the quality of the image representation. This redundancy is reduced e.g. with the help of a Huffman coding.
The basis for this coding is a code tree according to Huffman, which assigns short code words to symbols frequently used and long code words to symbols rarely used.
Beside Huffman coding another procedure is specified, which does not have a practical meaning because of the patent situation (arithmetic coding).
Additionally a special form of Run Length Encoding is applied.
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Entropy Coding 
Huffman Coding 
Subject: Huffman Coding 
Arithmetic Coding 
Subject: Arithmetic Coding 
Run Length Encoding (RLE) 
Subject: Run Length Encoding (RLE)