The Discrete Cosine Transform (

DCT) is a method of reformating data which helps separate an

image into

spectral sub-bands of differing importance. The DCT is similar to the Discrete

Fourier Transform (

DFT) in that it transforms a signal or image from the

spatial domain to the

frequency domain. However, the DCT does a better job of concentrating energy into lower order

coefficients the

DFT for

image data.

This is one part in several steps to generating a JPEG or MPEG compressed file.