;;---------- Inputs
reso: the resolution of the map in arcsec
map_in: the input unfiltered map
Npix: size of the map in pixel (assumes a squared map here)
;;---------- Read the transfer functions
tf = mrdfits(your_transfer_function_file, 1, head, /silent)
;;---------- Get a wave number array
kmax = 1.0/reso
karr = dist(Npix, Npix)
karr = karr/max(karr)*max(kmax)
;;---------- Get filtering mapping by interpolating the transfer
function
karr_lin = reform(karr, Npix*Npix)
filtering = interpol(tf.tf, tf.wave_number_arcsec, karr_lin)
filtering = reform(filtering, Npix, Npix)
;;---------- Apply the filtering
FT_map_in = FFT(map_in)
map_out = double(FFT(FT_map_in * filtering, /inverse))