Fast Discrete Cosine Transformation
Discrete cosine transform (DCT) is an important tool in the field of image processing.
DCT transforms a signal into the frequencies.
Many of the signal informations are transformed into low frequencies.
Thus, DCT is suitable for frequency filter.
This is the distionction of DCT.
I implemented two dimensional discrete cosine transform (DCT2D) and two dimensional inverse discrete cosine transform (IDCT2D).
You can confirm it by the code below.
library(devtools) install_github("ShotaOchi/imagerExtra") library(imagerExtra) layout(matrix(1:2, 1, 2)) g <- grayscale(boats) %>% plot(main = "Original") gg <- DCT2D(g) %>% IDCT2D() %>% plot(main = "Retransformed")
mean((g - gg)^2)