module 'cv2' has no attribute 'dwt2'

The error message "module 'cv2' has no attribute 'dwt2'" means that the OpenCV library (cv2) does not have a function or method called 'dwt2'.

The Discrete Wavelet Transform (DWT) is a signal processing technique that can be used for image compression, denoising, and feature extraction. If you want to use DWT in Python, you can try using other libraries such as PyWavelets or scipy.signal.

Here is an example of how to use PyWavelets to perform DWT on an image:

import cv2
import pywt

# Load an image
img = cv2.imread('image.jpg', cv2.IMREAD_GRAYSCALE)

# Perform DWT on the image using PyWavelets
coeffs = pywt.dwt2(img, 'haar')

# Extract the approximation, horizontal, and vertical coefficients
cA, (cH, cV) = coeffs

# Display the results
cv2.imshow('Original', img)
cv2.imshow('Approximation', cA)
cv2.imshow('Horizontal detail', cH)
cv2.imshow('Vertical detail', cV)
cv2.waitKey(0)
cv2.destroyAllWindows()

Note that you need to install PyWavelets first by running `pip install PyWavelets` in your terminal or command prompt.