fourier01_04.r

#reconstruct fourier transformed image from filtered spectrum:
re_construct <- cos(phase)*magni_filter
im_construct <- sin(phase)*magni_filter
mat_fft_construct <- matrix(complex(real = re_construct, imaginary = im_construct), nrow(mat_clown), ncol(mat_clown))

#Apply inversed Fourier transform to obtain the filtered image:
mat_clown_constr <- Re(fft(mat_fft_construct, inv = T))*checkerboard/prod(dim(mat_clown))

#normalize the resulting matrix between 0 and 1
mat_clown_constr <- (mat_clown_constr - min(mat_clown_constr)) /
                    (max(mat_clown_constr) - min(mat_clown_constr))

#save image after filtering:
con       <- file("clown_filtered.jpg", "wb")
clown_raw <- writeJPEG(rotate(rotate(rotate(mat_clown_constr))), raw(), quality = 0.7)
writeBin(clown_raw, con)
close(con)