The JPEG still picture compression standard
Communications of the ACM - Special issue on digital multimedia systems
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Discrete cosine transforms (DCTs) and discrete Fourier transforms (DFTs) are reviewed in order to determine why DCTs are more popular for image compression than the easier-to-compute DFTs. DCT-based image compression takes advantage of the fact that most images do not have much energy in the high-frequency coefficients. It is suggested that DCTs are more popular because fewer DCT coefficients than DFT coefficients are needed to get a good approximation to a typical signal, since the higher-frequency coefficients are small in magnitude and can be more crudely quantized than the low-frequency coefficients