fft_test.py

#!/usr/bin/python
# Abcdexter, 7/7/2021, 1142 
############################ 
# imports
############################
import sys
import numpy as np
from PIL import Image

import matplotlib.pyplot as plt
import scipy.fftpack



############################
# functions
############################


def cart2pol(x, y):
  '''
  :param x: x coordinate
  :param y: y coordinate
  :return: rho and phi as per polar coordinate (distance and angle)
  '''
  rho = np.sqrt(x**2 + y**2)
  phi = np.rad2deg(np.arctan2(y, x))
  # degrees is important
  return(rho, phi)


def pol2cart(rho, phi):
  '''
  :param rho: polar distance
  :param phi: counterclock angle from x axis
  :return: x,y coordinate
  '''
  phi = np.deg2rad(phi)
  x = rho * np.cos(phi)
  y = rho * np.sin(phi)
  return(int(x), int(y))


def iterate(img, X, Y, W, H):
  '''
  iterate 360 degrees
  '''
  R = []  # array of distances
  print(f"image is of size : {W}x{H}")
  
  count = 0
  s = 5
  for theta in range(0, 360*s):  # 0 to 2pi
    for r in range(1,2000):
      x, y = pol2cart(r, theta/s)
      px = x + X
      py = y + Y

      if (px < W) and (px >= 0) and (py < H) and (py >= 0) and img[px, py] == (0, 0, 0):
        R.append(r)
        break

  return R


############################
# main
############################


if __name__ == '__main__':

  USAGE = \
    '''
    Usage = python3 fft.py <img> [X] [Y] 
      img : absolute path of the image
      X   : X coordinate
      Y   : Y coordinate
    '''

  try:
    pic = Image.open(str(sys.argv[1])).convert('RGB')
    W, H = pic.size
    img = pic.load()

    X, Y = int(sys.argv[2]), int(sys.argv[3])

    R = iterate(img, X, Y, W, H)
    # R = R*5

    # Number of samplepoints
    N = len(R)
    # print(R)

    xf = np.linspace(0.0, N, N)
    yf = R #  scipy.fftpack.fft(R)

    fig, ax = plt.subplots()
    ax.plot(xf, yf)
    plt.show()

  except IndexError:
    print(USAGE)