_           _                 
 | |_ ___  __| |____  ___ _   _ 
 | __/ _ \/ _` |_  / / _ \ | | |
 | ||  __/ (_| |/ / |  __/ |_| |
  \__\___|\__,_/___(_)___|\__,_|

OpenCV Python experiments

#!/usr/bin/env python3

import cv2
import numpy as np

p1 = cv2.imread('q.png')
H,W = p1.shape[0],p1.shape[1]

p2 = np.full((H,W,3), 127, dtype=np.uint8)
for y in range(H):
    for x in range(W):
        for c in range(3):
            p2[y][x][0] = p1[y][x][0]
            p2[y][x][1] = p1[y][x][1]
            p2[y][x][2] = p1[y][x][2]

p2 = cv2.line(p2, (0, H//4), (W-1,H//4), (255,0,0), 1)

cv2.imshow('win',p2)
cv2.waitKey(0)
cv2.destroyAllWindows()

cv2.imwrite('p2.png', p2);

This is file qq.png:

This is file out.png: