How can I find the transform function, amplitude and frequency response of a digital filter in python?

Question

I have applied a laplace filter mask to an image and now I want to find the amplitude and freqency response of a laplacian filter: [[1,1,1], [1,-8,1], [1,1,1] ]. I know I need to first find the transfer function, however, I am unable to do this as well programatically in python.

Here is the code I have currently:

from matplotlib.pyplot import imread
import matplotlib.pyplot as plt 
from scipy.ndimage.filters import convolve 
import numpy as np 
import cv2 as cv


laplaceMask = np.array([ [1,1,1], [1,-8,1], [1,1,1] ]) 
img = imread("download.jpg") 

channels = [] 
for channel in range(3): 
    result = convolve(img[:,:,channel], laplaceMask) 
    channels.append(result) 

img = np.dstack((channels[0], channels[1], channels[2])) 

plt.imshow(img) 
plt.show() 

Answer 1

Assuming each element is the filter coefficients for the R, G, and B channels (I do not know if this is indeed the case here), you can get the frequency response of each channel using scipy.signal.freqz:

scipy.signal.freqz(c, 1, v)

Where c is the filter coefficients and v is the signal data for that channel.