MatplotlibMouseEventsRect.py

import cv2
import numpy as np
import matplotlib.pyplot as plt

colors = {'blue': (255, 0, 0), 'green': (0, 255, 0), 'red': (0, 0, 255), 'yellow': (0, 255, 255),
          'magenta': (255, 0, 255), 'cyan': (255, 255, 0), 'white': (255, 255, 255), 'black': (0, 0, 0),
          'gray': (125, 125, 125), 'rand': np.random.randint(0, high=256, size=(3,)).tolist(),
          'dark_gray': (50, 50, 50), 'light_gray': (220, 220, 220)}

image = np.zeros((400, 400, 3), dtype="uint8")
image[:] = colors['light_gray']

def UpdateImgWithMatplotlib():
    imgRGB = image[:, :, ::-1]
    plt.imshow(imgRGB)
    figure.canvas.draw()

def click_mouse_event(event):
    if event.dblclick and event.button == 1:
        cv2.rectangle(image, (int(round(event.xdata)), int(round(event.ydata))),
                      (int(round(event.xdata)) + 100, int(round(event.ydata)) + 50), colors['blue'], cv2.FILLED)
    UpdateImgWithMatplotlib()

figure = plt.figure()
figure.add_subplot(111)
UpdateImgWithMatplotlib()

figure.canvas.mpl_connect('button_press_event', click_mouse_event)
plt.show()