Many types of transforms used for picture coding, are Fourier, Karhonen-Loeve,
Walsh - Hadamard, lapped orthogonal, discrete cosine (DCT), and recently,
wavelets. The various transforms differ among themselves in three basic ways
that are of interest in picture coding:
1) The degree of concentration of energy in a few coefficients;
2) The region of influence of each coefficient in the reconstructed picture;
3) The appearance and visibility of coding noise due to coarse quantization of the
coefficients.