今天小编给大家分享一下Python怎么用cv2动态绘制圆和矩形的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。

本文可以实现在指定图片上动态绘制圆和矩形。

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()