先展示一下效果：

 英文输入法： y 代表绘制圆形； f 代表绘制方形； l 代表绘制直线（line）； c 代表清空画布

然后直接上代码：

import numpy as np
import matplotlib.pyplot as plt
import cv2 as cvimg = np.zeros((400,900,3), np.uint8)
cv.namedWindow('image')
cv.setMouseCallback('image', draw_circle)  # 将鼠标绘图事件与画布绑定在一起drawing = False
mode = 'f'   # f 表示方形   y 表示圆形  l 表示直线
color = (255,255,0)
ix, iy = -1, -1def draw_circle(event, x, y, flags, param):global ix, iy, drawing, mode, colorif event == cv.EVENT_LBUTTONDOWN:   # 鼠标左键按下  L：left  BUTTON: 点击  DOWN: 按下drawing = Trueix, iy = x, yelif event == cv.EVENT_MOUSEMOVE:  # 鼠标移动if drawing == True:if mode == 'f':cv.rectangle(img, (ix,iy), (x,y), color, -1)elif mode == 'y':cv.circle(img, (x,y), 20, color, -1)elif mode == 'l':cv.line(img, (ix,iy), (x,y), color, 10)elif event == cv.EVENT_LBUTTONUP:   # 鼠标左键松开drawing = Falseif mode == 'f':cv.rectangle(img, (ix,iy), (x,y), color, -1)elif mode == 'y':cv.circle(img, (x,y), 20, color, -1)elif mode == 'l':cv.line(img, (ix,iy), (x,y), color, 10)# 创建滑动条
cv.createTrackbar('R','image',0,255,nothing)
cv.createTrackbar('G','image',0,255,nothing)
cv.createTrackbar('B','image',0,255,nothing)while(1):cv.imshow('image',img)k = cv.waitKey(1) & 0xFFif k == ord('f'):mode = 'f'elif k == ord('y'):mode = 'y'elif k == ord('l'):mode = 'l'elif k == ord('c'):img[:] = 0elif k == 27:break# 获取滑动条的位置（既 RGB 每个滑动条的值）r = cv.getTrackbarPos('R','image')g = cv.getTrackbarPos('G','image')b = cv.getTrackbarPos('B','image')color = (b,g,r)cv.destroyAllWindows()