opencv 矩形标记

import cv2
from PIL import Image
import pytesseract
import pyautogui
import numpy as np
import time
#图片路径
img = cv2.imread('Images/CAD2.png')

xstart, ystart = 0, 0 #起始点x,y坐标
xend, yend = 0, 0#鼠标松开后 x,y坐标
px, py = 0, 0#移动时的x,y坐标

def on_EVENT_LBUTTONDOWN(event, x, y,flags, param):
    global xstart, ystart, px, py, xend, yend
    img2 = img.copy() #复制一个图片
    if event == cv2.EVENT_LBUTTONDOWN:  #鼠标点击时的操作
        xstart = x;
        ystart = y;
        cv2.imshow('image', img2)
    elif event == cv2.EVENT_MOUSEMOVE and (flags & cv2.EVENT_FLAG_LBUTTON): #鼠标移动时的操作
        px, py = x, y
        #在复制图片上进行鼠标移动时的画矩形框的操作
        cv2.rectangle(img2, (xstart, ystart), (x, y), (0, 0, 255), 2)
        cv2.imshow('image', img2)
    elif event==cv2.EVENT_LBUTTONUP: #鼠标抬起时的操作
        xend = x;
        yend = y;
        if (xstart != xend and ystart != yend):
            #矩形框
            cv2.rectangle(img, (xstart, ystart), (xend, yend), (0, 0, 255), 2)

            ## 矩形截图
            # t = time.time()
            # mst = int(round(t * 1000));# 生成毫秒时间戳 13位
            ## opencv区域截图标记参数
            ## xstart: 区块左上角位置的像素点离图片左边界的距离
            ## ystart：区块左上角位置的像素点离图片上边界的距离
            ## xend：区块右下角位置的像素点离图片左边界的距离
            ## yend：区块右下角位置的像素点离图片上边界的距离
            #cropped = img[ystart:yend, xstart:xend]
            #imgstr = "Screenshot_Image/" + str(mst) + ".png";  # 根据时间戳生成一个图片名称
            ## 保存截图
            #cv2.imwrite(imgstr, cropped)

            # 显示图片
            cv2.imshow('image', img)

cv2.namedWindow("image")
cv2.setMouseCallback("image", on_EVENT_LBUTTONDOWN)
cv2.imshow("image", img)
cv2.waitKey(0)