(n) ¶Return the DCT transformation matrix of size n-by-n.
If A is an n-by-n matrix, then the following are true:
T*A == dct(A), T'*A == idct(A)
T*A*T' == dct2(A), T'*A*T == idct2(A)
A DCT transformation matrix is useful for doing things like jpeg image compression, in which an 8x8 DCT matrix is applied to non-overlapping blocks throughout an image and only a subblock on the top left of each block is kept. During restoration, the remainder of the block is filled with zeros and the inverse transform is applied to the block.
See also: dct, idct, dct2, idct2.
Package: signal