Huffman compressionAlso known as Huffman encoding, an algorithm for the lossless compression of files based on the frequency of occurrence of a symbol in the file that is being compressed. The Huffman algorithm is based on statistical coding, which means that the probability of a symbol has a direct bearing on the length of its representation. The more probable the occurrence of a symbol is, the shorter will be its bit-size representation. In any file, certain characters are used more than others. Using binary representation, the number of bits required to represent each character depends upon the number of characters that have to be represented. Using one bit we can represent two characters, i.e., 0 represents the first character and 1 represents the second character. Using two bits we can represent four characters, and so on.
Unlike ASCII code, which is a fixed-length code using seven bits per character, Huffman compression is a variable-length coding system that assigns smaller codes for more frequently used characters and larger codes for less frequently used characters in order to reduce the size of files being compressed and transferred.
For example, in a file with the following data:
the frequency of "X" is 6, the frequency of "Y" is 4, and the frequency of "Z" is 2. If each character is represented using a fixed-length code of two bits, then the number of bits required to store this file would be 24, i.e., (2 x 6) + (2x 4) + (2x 2) = 24.
If the above data were compressed using Huffman compression, the more frequently occurring numbers would be represented by smaller bits, such as:
X by the code 0 (1 bit)
Y by the code 10 (2 bits)
Z by the code 11 (2 bits)
therefore the size of the file becomes 18, i.e., (1x 6) + (2 x 4) + (2 x 2) = 18.
In the above example, more frequently occurring characters are assigned smaller codes, resulting in a smaller number of bits in the final compressed file.
Huffman compression was named after its discoverer, David Huffman.
- Watch Datamation's editor James Maguire moderate roundtable discussions with tech experts from companies such as Accenture, Dell, Blue Jeans Network, Microsoft and more »
Tape clearly is on the decline. But remember, legacy systems can hang for a shockingly long time. Read More »Apple Pay Promises to Strengthen Payment Security
Experts believe that Apple Pay and other competitive payment systems will be far more secure than cards, even cards equipped with EMV chips. Read More »Internet of Things Shaping IT's Future
To make the IoT both work and pay off, IT is juggling upgrading and building app-centric networks, mapping out new data center architectures and... Read More »
The trend for the past two years has been for shoppers to spend more online during the holiday season. How do you typically shop for holiday... Read More »How to Create a Desktop Shortcut to a Website
This Webopedia guide will show you how to create a desktop shortcut to a website using Firefox, Chrome or Internet Explorer (IE). Read More »Flash Data Storage Vendor Trends
Although it is almost impossible to keep up with the pace of ongoing product releases, here are three recent highlights in the flash data storage... Read More »