# Last edited on 2021-07-31 12:02:15 by jstolfi

from math import sin, cos, pi
from basis_sample import basis_sample

def basis_2d_hartley_sample(fr, s):
  # Samples at the sample points {s} the 2d Hartley basis functions whose
  # frequency vectors are in the list {fr}. 
  # 
  # Each frequency vector {fr[i]} should be a 2-tuple of signed ints. 
  # Each sample point {s[k]} should be a 2-tuple of floats.
  #
  # Returns a list {B} of {nf} lists, each element being a list of
  # {ns=len(s)} floats; such that {B[i][k]} is the 2d Hartley basis
  # element with frequency {fr[i]} evaluated at the point {s[k]}.
  
  nb = len(fr)
  
  def basis_hartley(i, p):
    fxi, fyi = fr[i]
    ang = (p[0]*fxi + p[1]*fyi + 0.25)*pi
    Bp = 0.5*(1 + cos(ang))
    return Bp;
    # ......................................................................
    
  B = basis_sample(nb, basis_hartley, s);
  return B
  # ----------------------------------------------------------------------