画矩形

import cv2image = cv2.imread('1.jpg')cv2.rectangle(image, (xmin, ymin), (xmax, ymax), (0, 0, 255), 2) cv2.imwrite('2.jpg', image)

画圆点:

point_size = 1point_color = (0, 0, 255) # BGRthickness = 4 # 可以为 0 、4、8for point in points:x1,y1=pointcv2.circle(img, (int(x1),int(y1)), point_size, point_color, thickness)

外接矩形，最小外接矩形，cnt其实就是轮廓坐标：

import osimport cv2import joblibimport numpy as npimage=cv2.imread("first.jpg")roi=np.array([[10,10],[100,20],[100,150],[20,80]])x, y, w, h = cv2.boundingRect(roi)cv2.rectangle(image, (x, y), (x + w, y + h), (0, 255, 0), 2)# 最小外接矩形框，有方向角rect = cv2.minAreaRect(roi)box = cv2.boxPoints(rect)box = np.int0(box)cv2.drawContours(image, [box], 0, (0, 0, 255), 2)

以下内容转自：

OpenCv-Python 最小外接圆、最小外接矩形、椭圆拟合、直线拟合_牧野的博客-CSDN博客

最小外接圆、最小外接矩形、椭圆拟合、直线拟合

#coding: utf-8import cv2import numpy as npimport imutilsim = cv2.imread('./5121.png')imgray = cv2.cvtColor(im,cv2.COLOR_BGR2GRAY)ret,thresh = cv2.threshold(imgray,0,255,cv2.THRESH_BINARY+cv2.THRESH_OTSU) # 大津阈值contours = cv2.findContours(thresh,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_NONE) #cv2.RETR_EXTERNAL 定义只检测外围轮廓cnts = contours[0] if imutils.is_cv2() else contours[1] #用imutils来判断是opencv是2还是2+for cnt in cnts:# 外接矩形框，没有方向角x, y, w, h = cv2.boundingRect(cnt)cv2.rectangle(im, (x, y), (x + w, y + h), (0, 255, 0), 2)# 最小外接矩形框，有方向角rect = cv2.minAreaRect(cnt)box = cv2.cv.Boxpoints() if imutils.is_cv2()else cv2.boxPoints(rect)box = np.int0(box)cv2.drawContours(im, [box], 0, (0, 0, 255), 2)# 最小外接圆(x, y), radius = cv2.minEnclosingCircle(cnt)center = (int(x), int(y))radius = int(radius)cv2.circle(im, center, radius, (255, 0, 0), 2)# 椭圆拟合ellipse = cv2.fitEllipse(cnt)cv2.ellipse(im, ellipse, (255, 255, 0), 2)# 直线拟合rows, cols = im.shape[:2][vx, vy, x, y] = cv2.fitLine(cnt, cv2.DIST_L2, 0, 0.01, 0.01)lefty = int((-x * vy / vx) + y)righty = int(((cols - x) * vy / vx) + y)im = cv2.line(im, (cols - 1, righty), (0, lefty), (0, 255, 255), 2)cv2.imshow('a',im)cv2.imwrite('./result.jpg',im)cv2.waitKey(0)