Compression

Definition

Data compression is decreasing the size of a file. There are many different compression techniques.

Lossy Compression

Lossy compression is a compression technique that decreases file size by discarding bits of unnecessary data. This means that the original file cannot be recreated. An example of lossy compression is JPEG. JPEG images can discard some of the original data to create a new image which is similar to the original, but has a reduced resolution.

Lossless Compression

Lossless compression is a compression technique that decreases file size whilst keeps all of the data. This is possible because of repeating patterns. Also, this means that the original file can be recreated to the same quality. Examples of lossless compression are Run Length Encoding and Dictionary Based Methods. Run Length Encoding replaces repeating pixels or codes. Dictionary Based Methods rely on patterns within a file and are more effective with larger files. Each pattern can has an ID number.

Run Length Encoding

Run length encoding is a type of compression typically used for bitmap images.

Dictionary Based Methods

Dictionary based methods are used to compress text files

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