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| JPEG (Joint Photographic Experts Group) |  |
Expert Lossy Compression: There are encoding processes which guarantee a high compression ratio for any image, but at the expense of lost of information. these processes use the fact that human beings have only a restriced capability to perceive high frequences. Images reduced from their high frequent elements may have a high degree of quality while being compressed quite considerably.
To decrease the high frequencies the data must be sorted by frequencies. That can be accomplished by a transformation from the time space to the frequency space. In this way the values of the high frequencies can be changed to 0. The two common processes are the Discrete Cosine Transformation (DCT) and the Fast Fourier Transformation (FFT).
Formula of DCT: