Rectangular Doodle Sketchpad

Save it for now, if you have time to study

Write a rectangular graffiti drawing board to achieve the function:

Press and drag the left mouse button to draw a rectangle, when the left mouse button pops up to complete the drawing
Press the 'c' key to clear the artboard
Press the 'ESC' key to exit

import numpy as np
import cv2 as cv
from random import randint


class Painter:
    def __init__(self) -> None:
        self.mouse_is_pressed = False
        self.last_pos = (-1, -1)
        self.width = 500
        self.height = 500
        self.img = np.zeros((self.width, self.height, 3), np.uint8)
        self.window_name = 'painter'
        self.color = None

    def run(self):
        print('画板，拖动鼠标绘制矩形框，按ESC退出，按c键清空画板')
        # 框随意变大小
        cv.namedWindow(self.window_name)
        # 鼠标响应
        cv.setMouseCallback(
            self.window_name,
            lambda event, x, y, flags, param: self.on_draw(
                event, x, y, flags, param
            )
        )
        while True:
            cv.imshow(self.window_name, self.img)
            k = cv.waitKey(1) & 0xFF
            if k == ord('c'):
                self.clean()
            elif k == 27:
                break

        cv.destroyAllWindows()

    def on_draw(self, event, x, y, flags, param):
        # TODO(You): 请正确实现画板事件响应，完成功能
        pos = (x, y)
        if event == cv.EVENT_LBUTTONDOWN:
            self.mouse_is_pressed = True
            self.last_pos = pos
        elif event == cv.EVENT_MOUSEMOVE:
            if self.mouse_is_pressed == True:
                self.begin_draw_rectangle(self.last_pos, pos)
        elif event == cv.EVENT_LBUTTONUP:
            self.end_draw_rectangle(self.last_pos, pos)
            self.mouse_is_pressed = False

    def clean(self):
        cv.rectangle(self.img, (0, 0), (self.height, self.width), (0, 0, 0), -1)

    def begin_draw_rectangle(self, pos1, pos2):
        if self.color is None:
            self.color = (randint(0, 256), randint(0, 256), randint(0, 256))
        cv.rectangle(self.img, pos1, pos2, self.color, -1)

    def end_draw_rectangle(self, pos1, pos2):
        self.color = None


if __name__ == '__main__':
    p = Painter()
    p.run()