#### Gabor Filter

R
```# Implementation of the Gaborfilter
# https://en.wikipedia.org/wiki/Gabor_filter
import numpy as np
from cv2 import COLOR_BGR2GRAY, CV_8UC3, cvtColor, filter2D, imread, imshow, waitKey

def gabor_filter_kernel(
ksize: int, sigma: int, theta: int, lambd: int, gamma: int, psi: int
) -> np.ndarray:
"""
:param ksize:   The kernelsize of the convolutional filter (ksize x ksize)
:param sigma:   standard deviation of the gaussian bell curve
:param theta:   The orientation of the normal to the parallel stripes
of Gabor function.
:param lambd:   Wavelength of the sinusoidal component.
:param gamma:   The spatial aspect ratio and specifies the ellipticity
of the support of Gabor function.
:param psi:     The phase offset of the sinusoidal function.

>>> gabor_filter_kernel(3, 8, 0, 10, 0, 0).tolist()
[[0.8027212023735046, 1.0, 0.8027212023735046], [0.8027212023735046, 1.0, \
0.8027212023735046], [0.8027212023735046, 1.0, 0.8027212023735046]]

"""

# prepare kernel
# the kernel size have to be odd
if (ksize % 2) == 0:
ksize = ksize + 1
gabor = np.zeros((ksize, ksize), dtype=np.float32)

# each value
for y in range(ksize):
for x in range(ksize):
# distance from center
px = x - ksize // 2
py = y - ksize // 2

_theta = theta / 180 * np.pi
cos_theta = np.cos(_theta)
sin_theta = np.sin(_theta)

# get kernel x
_x = cos_theta * px + sin_theta * py

# get kernel y
_y = -sin_theta * px + cos_theta * py

# fill kernel
gabor[y, x] = np.exp(-(_x**2 + gamma**2 * _y**2) / (2 * sigma**2)) * np.cos(
2 * np.pi * _x / lambd + psi
)

return gabor

if __name__ == "__main__":
import doctest

doctest.testmod()
# turn image in gray scale value
gray = cvtColor(img, COLOR_BGR2GRAY)

# Apply multiple Kernel to detect edges
out = np.zeros(gray.shape[:2])
for theta in [0, 30, 60, 90, 120, 150]:
"""
ksize = 10
sigma = 8
lambd = 10
gamma = 0
psi = 0
"""
kernel_10 = gabor_filter_kernel(10, 8, theta, 10, 0, 0)
out += filter2D(gray, CV_8UC3, kernel_10)
out = out / out.max() * 255
out = out.astype(np.uint8)

imshow("Original", gray)
imshow("Gabor filter with 20x20 mask and 6 directions", out)

waitKey(0)
```