How to draw dynamic circles and rectangles using the cv2 library in Python

This article can dynamically draw circles and rectangles on specified pictures.

import cv2
import numpy as np
import copy
 
class Rect(object):
 
    #创建一个类用于接收鼠标点击产生的数据坐标点。
 
    def __init__(self):
 
        self.t1 = (0,0)
 
        self.br = (0,0)
 
        self.r = 0
 
    def regularize(self):
 
        pt1 = (min(self.t1[0],self.br[0]),min(self.t1[1],self.br[1]))
 
        br1 = (max(self.t1[0],self.br[0]),max(self.t1[1],self.br[1]))
 
        self.t1 = pt1
 
        self.br = br1
 
 
class DrawRects(object):
 
    def __init__(self,img,color = (0,255,0),thickness = 3):
 
        self.img = img
 
        self.image_for_show = img.copy()
 
        '''
        用于覆盖之前的图片，然后在新的空白图片上将以前绘制的图片和目前最新的图片
        绘制的到新的图片上。
        '''
        
        self.color = color
 
        self.thickness = thickness
 
        self.left_button_down = False #用于判断左键是否按下。
 
        self.current_rect = Rect() #用于接收最新绘制的图形。
 
        self.rects = [] #用于接收绘制的矩形数据。
 
        self.circles = [] #用于接收绘制的圆数据
 
 
    @staticmethod
    def __clip(value,low,high):
 
        output = max(value,low)
 
        output = min(output,high)
 
        return output
 
    def shrink_point(self,x,y):
 
        height,width = self.image_for_show.shape[0:2]
 
        x_shrink = self.__clip(x,0,width)
 
        y_shrink = self.__clip(y,0,height)
 
        return (x_shrink,y_shrink)
 
    '''
    上述方法用于限制鼠标点击产生的数据在图片范围内。
    '''
 
    def reset_image(self):
 
        self.image_for_show = self.img.copy()
 
    def append(self):
 
        if draw_circle_now:
 
            self.rects.append(['c',copy.deepcopy(self.current_rect)])
 
        else:
 
            self.rects.append(['r',copy.deepcopy(self.current_rect)])
 
 
 
    def draw(self):
 
        for rect in self.rects:
 
            if rect[0] == 'r':
 
                cv2.rectangle(self.image_for_show,rect[1].t1,rect[1].br,color = self.color,thickness=self.thickness)
 
            elif rect[0] == 'c':
 
                cv2.circle(self.image_for_show,rect[1].t1,rect[1].r,color = self.color,thickness = self.thickness)
        
    def cal_R(self):
 
        self.current_rect.r = int((abs(self.current_rect.br[0] - self.current_rect.t1[0])**2 + abs(self.current_rect.br[1] - self.current_rect.t1[1])**2)**0.5)
 
        #print(self.current_circle.r)
 
        return self.current_rect.r
 
 
    def draw_current_rect(self):
 
        if draw_circle_now:
 
            self.current_rect.r = self.cal_R()
 
            cv2.circle(self.image_for_show,self.current_rect.t1,self.current_rect.r,color = self.color,thickness=3)
 
        else:
 
            cv2.rectangle(self.image_for_show,self.current_rect.t1,self.current_rect.br,
                      color = self.color,thickness = self.thickness)
 
    def pop(self):
 
        rect = Rect()
 
        if self.rects:
 
            rect = self.rects.pop()
 
        return rect
 
 
def onmouse_draw_rect(event,x,y,flags,draw_rects):
 
    if event == cv2.EVENT_LBUTTONDOWN:
 
        draw_rects.left_button_down = True
 
        draw_rects.current_rect.t1 = (x,y)
 
    if draw_rects.left_button_down  and event == cv2.EVENT_MOUSEMOVE:
 
        draw_rects.current_rect.br = draw_rects.shrink_point(x,y)
 
        draw_rects.reset_image()
 
        draw_rects.draw()
 
        draw_rects.draw_current_rect()
 
    if event == cv2.EVENT_LBUTTONUP:
 
        draw_rects.left_button_down = False
 
        draw_rects.current_rect.br = draw_rects.shrink_point(x,y)
 
        #draw_rects.current_rect.regularize()
 
        draw_rects.append()
 
    if (not draw_rects.left_button_down) and  event == cv2.EVENT_RBUTTONDOWN:
 
        draw_rects.pop()
 
        draw_rects.reset_image()
 
        draw_rects.draw()
 
 
 
 
draw_circle_now = False
 
img = np.zeros((516,516,3),np.uint8)
 
draw_rects = DrawRects(img,(0,255,255))
 
cv2.namedWindow('image')
 
cv2.setMouseCallback('image',onmouse_draw_rect,draw_rects)
 
while True:
 
    cv2.imshow('image',draw_rects.image_for_show)
 
    key = cv2.waitKey(30)
 
    if key == ord('c'):
 
        draw_circle_now = not draw_circle_now
 
    elif key == 27:
 
        break
 
cv2.destroyAllWindows()

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