opencv例子 鼠标画圆

窗口与鼠标事件绑定
cv.setMouseCallback(windowName, MouseCallback, param=None)
windowName：窗口名称
MouseCallback：鼠标响应回调函数
param：响应函数传递的的参数
代码如下：
import cv2 as cv
import numpy as np

def draw_circle(event, x, y, flags, param): #画圆
if event == cv.EVENT_LBUTTONDBLCLK: # cv.EVENT_LBUTTONDOWN = 1, 左键按下
cv.circle(img, (x, y), 100, (255, 0, 0), -1)
img = np.zeros((512, 512, 3), np.uint8) #创建黑色图片
cv.namedWindow(‘image’)
cv.setMouseCallback(‘image’, draw_circle)
while(1):
cv.imshow(‘image’, img)
if cv.waitKey(20) & 0xFF==27:
break
cv.destroyAllWindows()

双击鼠标左键：