opencv dynamic drawing

Go directly to the code, there is nothing to say

import math
import cv2 as cv
import numpy as np

tangle = [0, 0, 0, 0]
start = [0, 0]
click = False
change='l'
def draw(path):
    global change
    cv.namedWindow('1', 0)
    cv.resizeWindow('1', 600, 600)
    cv.setMouseCallback('1', call_back)
    while cv.waitKey(1) != 27:
# Esc
        img = cv.imread(path)
        pt1 = (tangle[0], tangle[1])
        pt2 = (tangle[2], tangle[3])
        center=[int((tangle[0] + tangle[2]) / 2), int((tangle[1] + tangle[3]) / 2)]
# 求圆的中心点
        r=(tangle[2]-tangle[0])**2+(tangle[3]-tangle[1])**2
# 求圆的半径
        radius=int(math.sqrt(r)/2)
        if change=='l':
# change='l',画直线
            cv.line(img, pt1, pt2, (255, 0, 0), 2)
            cv.imshow('1', img)
        elif change=='r':
# change='r',画圆
            cv.circle(img,center,radius,(255,0,0),2)
            cv.imshow('1', img)
# change='t',画矩形
        elif change=='t':
            cv.rectangle(img, pt1, pt2, (255, 0, 0), 2)
            cv.imshow('1', img)
# 回调函数
def call_back(event, x, y, flags, param):
    global click,change
# 按下左键
    if event == cv.EVENT_LBUTTONDOWN:
        start[0] = x
        start[1] = y
        click = True
# 移动
    if event == cv.EVENT_MOUSEMOVE:
        if click:
            tangle[0] = start[0]
            tangle[1] = start[1]
            tangle[2] = x
            tangle[3] = y
# 释放
    if event == cv.EVENT_LBUTTONUP:
        left_palce = (tangle[0], tangle[1])
        right_palce = (tangle[2], tangle[3])
        click = False
# 左击两次，从键盘输入,改变change
    if event==cv.EVENT_LBUTTONDBLCLK:
        key=cv.waitKey(0)
        if key==ord('l'):
            change='l'
        elif key==ord('r'):
            change='r'
        elif key==ord('t'):
            change='t'

operate

draw('1.jpg')
# 运行函数

starting time

The default is to draw lines (parameters and the like can be set by yourself)

Double-click the left button and press r on the keyboard. At this time, the double-click event is called, change='r', at this time

When I draw a picture again, I draw a circle, which is dynamic.

In the same way, double-click and press t to draw a rectangle

Summarize

There are also irregular shapes drawn every time.

If you draw a rectangle on the picture, you can use selectROI to cut it out. What if it is a circle or an irregular picture?

Cut?