cv2 canvas

cv2_canvas.py

import cv2
import numpy as np

size = 28
drawing = False
win_name = "Draw digit"

def draw(event, x, y, flags, *param):
    global drawing
    if event == cv2.EVENT_LBUTTONDOWN:
        drawing = not drawing
    elif event == cv2.EVENT_MOUSEMOVE and drawing:
        img[y, x] = 255
        cv2.imshow(win_name, img)

img = np.zeros((size, size)).astype(np.uint8)
cv2.namedWindow(win_name)
cv2.setMouseCallback(win_name, draw)

while(1):
    cv2.imshow(win_name, img)
    k = cv2.waitKey(0)
    if k == 27:
        break
    if k == ord('c'):
        img.fill(0)
    if k == ord(' '):
        print('ok')

cv2.destroyAllWindows()