Definition: Lossless compression; Lossless format;

Definition: Lossless compression; Lossless format;  | Glossary entry

Lossless compression; Lossless format;

The ‘Lossless compression’ format is a form of compression for data files that ensure the original data is available on decompression but still reduces its size for storage. Thus the file size is smaller than the uncompressed original file and none of the data is discarded as it is with the ‘lossy compression‘ method. The lossless compression process can involve a whole range of different computing processes to create a model of the original data. However, the model can be used to recreate the original data in full. Lossless compression is therefore non-destructive of data.

Lossless data compression is used when it is important that the original data can be reconstructed in full without errors. It is also sometimes used with lossy compression. The partnership of the two classes of compression can lead to significant reductions in the size of files.

Lossless compression is frequently applied to RAW files in digital photography. It is important that RAW files do not lose any data to ensure that full flexibility in post processing is retained. High efficiency lossless compression is therefore important since RAW files contain a great deal of data. This means they are often large and difficult to store which is an impairment. The application of an efficient compression method retaining all data after decompression is very important. Such compression would aid storage of the file, speed up transmission and make archiving more economical.

Many different image file formats can use lossless compression to compress the file. Notable are TIFF, JPEG200, DNG, PNG and some proprietary manufacturer file formats.

Lossless compression routines are supplied with many image applications and image editors. However, some specialized applications are used in conjunction with the file itself.

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