Monday, July 23, 2007


  • DCT is a Fourier-related transform similar to DFT, but using only real number.
  • DCT is similar to the Fast Fourier Transform (FFT), but can approximate lines well with fewer coefficients (see following figure, the effect after IDCT and IDFT).
  • The DCT concentrates most of the power on the lower frequencies.




DCTs use only cosine functions, while DFTs use both cosine and sine functions.
The two-dimensional DCT is:

X_k = \sum _{n_1 = 0}^{N_1-1} \sum _{n_2 = 0}^{N_2-1} x_{n1}x_{n2}\cos \frac{\pi(n_1 + \frac{1}{2}k_1)}{N_1} \cos \frac{\pi(n_2 + \frac{1}{2}k_2)}{N_2}

some of above are from

No comments:

Post a Comment