COMPRESSION ALGORITHMS COMPARED

The following data compression algorithms were compared for compression ratio and time for compression on a variety of raw detector images from different scientific fields. This work was carried out by Ulrike Willms.

• B.O. : The imgCIF / CBF Byte Offset algorithm
• B.O/pack : B.O. followed by pack
• B.O/gzip : B.O. folowed by gzip
• JPA : Jan Pieter Abraham's algorithm, which is predictor 4, followed by variable length non-entropy encoding with a variable number of bits
• pack : Huffman encoding
• compress : Lempel-Ziv dictionary encoding.
• gzip : Variation of LZ77 dictionary encoding.
• bzip : Runlength, Burrow-Wheeler-Fenwick block sorting, move-to-front , and arithmetic encoding.
• bwt : As bzip, but the order of the operations may be varied.
• ha 1 : Dictionary encoding followed by arithmetic encoding
• ha 2 : Finite context model (sohisticated predictor) followed by arithmetic encoding.
• ljpg : Variable predictor followed by Huffman encoding (The JPEG standard also has an arithmetic encoding option.)
• btpc : Hierarchical image pyramid followed by Huffman encoding
• shorten : More complicated predictor followed by Huffman encoding.
• freeze : Lemple-Ziv dictionary encoding, followed by adaptive Huffman encoding.
• Pre Huff : Predictor 4 followed by modified Huffman encoding using 256 codes.