pickle2_unpickle3.py

#pickle dict with image in Python2 (2.7.6 used)
frame = cv2.imread('input.jpg')
img_str = cv2.imencode('.jpg', frame)[1].tostring()
data = {'img': img_str}
with open('pickledObj.pkl', 'wb') as outfile:
  pickle.dump(data, outfile)
  
# unpickle in Python3 (Python 3.4.3 used for testing) using encoding=latin1
with open('pickledObj.pkl', 'rb') as f:
        data_dict = pickle.load(f, encoding='latin1')
img_str = data_dict['img']
img = np.fromstring(img_str, dtype='uint8')
img = cv2.imdecode(img, cv2.IMREAD_UNCHANGED)
cv2.imwrite('latin_output.jpg', img)) # This will be a corrupted image

# unpickle in Python3 encoding=bytes
with open('pickledObj.pkl', 'rb') as f:
        data_dict = pickle.load(f, encoding='bytes')
img_str = data_dict[b'img']
img = np.fromstring(img_str, dtype='uint8')
img = cv2.imdecode(img, cv2.IMREAD_UNCHANGED)
cv2.imwrite('output.jpg', img) # Retrieves the original image

Issues when unpickling a Python2 pickle object in Python3

https://stackoverflow.com/a/47882939/5774004