cv2.imencode may help you:
import numpy as np
import cv2
import io
img = np.ones((100, 100), np.uint8)
# encode
is_success, buffer = cv2.imencode(".jpg", img)
io_buf = io.BytesIO(buffer)
# decode
decode_img = cv2.imdecode(np.frombuffer(io_buf.getbuffer(), np.uint8), -1)
print(np.allclose(img, decode_img)) # True