鼠标作为画笔

opencv处理鼠标事件。cv.setMouseCallback()

查询所有可用的事件

import cv2 as cv
events=[i for i in dir(cv) if 'EVENT' in i]
print(events)

双击鼠标绘制一个圆

import numpy as np
import cv2 as cv

def draw_circle(event,x,y,flags,param):
    if event==cv.EVENT_LBUTTONDBLCLK:
        cv.circle(img,(x,y),100,(0,0,255),-1,cv.LINE_AA)

img=np.zeros((512,512,3),np.uint8)
cv.namedWindow('image',cv.WINDOW_NORMAL)
# 给窗口绑定鼠标事件
cv.setMouseCallback('image',draw_circle)
while(1):
    cv.imshow('image',img)
    # 按ESC退出
    if cv.waitKey(1)&0XFF==27:
        break
cv.destroyAllWindows()

拖动鼠标绘制矩形或圆形

import cv2 as cv
import numpy as np

drawing=False
mode=True # 如果为真则绘制矩形
ix,iy=-1,-1
def draw_circle(event,x,y,flags,param):
    global ix,iy,drawing,mode
    if event==cv.EVENT_LBUTTONDOWN:
        drawing=True
        ix,iy=x,y
    elif event==cv.EVENT_MOUSEMOVE:
        if drawing==True:
            if mode==True:
                cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)
            else:
                cv.circle(img,(x,y),5,(0,0,255),-1)
    elif event==cv.EVENT_LBUTTONUP:
        drawing=False
        if mode==True:
            cv.rectangle(img,(ix,iy),(x,y),(0,255,0),-1)
        else:
            cv.circle(img,(x,y),5,(0,0,255),-1)

img=np.zeros((512,512,3),np.uint8)
cv.namedWindow('img')
cv.setMouseCallback('img',draw_circle)
while True:
    cv.imshow('img',img)
    if cv.waitKey(1)&0XFF==27:
        break
cv.destroyAllWindows()