04_Paintbrush.py

import cv2
import numpy as np

# list all available events available
events = [i for i in dir(cv2) if 'EVENT' in i]
print(events)

# mouse callback function -  It draws a circle where we double-click.
def draw_circle(event, x, y, flags, param):
    if event == cv2.EVENT_LBUTTONDBLCLK:
        cv2.circle(img, (x, y), 100, (255, 0, 0), -1)


# Create a black image, a window and bind the function to window
img = np.zeros((512, 512, 3), np.uint8)
cv2.namedWindow('image')
cv2.setMouseCallback('image', draw_circle)

while(1):
    cv2.imshow('image', img)
    if cv2.waitKey(20) & 0xFF == 27:
        break
cv2.destroyAllWindows()

# MORE ADVANCED DEMO
drawing = False # true if mouse is pressed
mode = True # if True, draw rectangle. Press 'm' to toggle to curve
ix, iy = -1, -1

# mouse callback function - It draws  circle and Rectangle(Toggle 'm' for rectangle).
def draw_circle(event, x, y, flags, param):
    global ix, iy, drawing, mode

    if event == cv2.EVENT_LBUTTONDOWN:
        drawing = True
        ix, iy = x, y

    elif event == cv2.EVENT_MOUSEMOVE:
        if drawing == True:
            if mode == True:
                cv2.rectangle(img, (ix, iy), (x, y), (0, 255, 0), -1)
                """
                # TO DRAW UNFILLED RECTANGLE-- And also change the thickness above to he positive values.
                a=x
                b=y
                if a != x | b != y:
                    cv2.rectangle(img,(ix,iy),(x,y),(0,0,0),-1)
                """ 
            else:
                cv2.circle(img, (x, y), 5, (0, 0, 255), -1)

    elif event == cv2.EVENT_LBUTTONUP:
        drawing = False
        if mode == True:
            cv2.rectangle(img, (ix, iy), (x, y), (0, 255, 0), -1)
        else:
            cv2.circle(img, x, y), 5, (0, 0, 255), -1)


img = np.zeros((512, 512, 3), np.uint8)
cv2.namedWindow('image')
cv2.setMouseCallback('image', draw_circle)

while(1):
    cv2.imshow('image', img)
    k = cv2.waitKey(1) & 0xFF
    if k == ord('m'):                                    # Set a keyboard binding for key ‘m’ to toggle between rectangle and circle.
        mode = not mode
    elif k == 27:
        break

cv2.destroyAllWindows()