玩了下opencv的aruco（python版）

简单的玩了下opencv里头的aruco，用的手机相机，手机装了个 ip摄像头，这样视频就可以传到电脑上了。

首先是标定，我没打印chessboard，直接在电脑屏幕上显示，拍了17张，大概如下：

又在手机上装了个 尺子 之类的app，比划着量了下，每个格子大概是18.1 mm，这个棋盘是10 x 7的棋盘。

要pip install opencv-contrib-python才有扩展模块，扩展模块中包含aruco

然后标定了一下：

 import cv2
 import numpy as np
 import glob
 import matplotlib.pyplot as plt
 import matplotlib.patches as patches

 # 找棋盘格角点

 criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.001) # 阈值
 #棋盘格模板规格
 w = 9   # 10 - 1
 h = 6   # 7  - 1
 # 世界坐标系中的棋盘格点,例如(0,0,0), (1,0,0), (2,0,0) ....,(8,5,0)，去掉Z坐标，记为二维矩阵
 objp = np.zeros((w*h,3), np.float32)
 objp[:,:2] = np.mgrid[0:w,0:h].T.reshape(-1,2)
 objp = objp*18.1  # 18.1 mm

 # 储存棋盘格角点的世界坐标和图像坐标对
 objpoints = [] # 在世界坐标系中的三维点
 imgpoints = [] # 在图像平面的二维点

 images = glob.glob('./chessboard/*.jpg')  #   拍摄的十几张棋盘图片所在目录

 i = 1
 for fname in images:

     img = cv2.imread(fname)
     gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
     # 找到棋盘格角点
     ret, corners = cv2.findChessboardCorners(gray, (w,h),None)
     # 如果找到足够点对，将其存储起来
     if ret == True:
         print("i:", i)
         i = i+1

         cv2.cornerSubPix(gray,corners,(11,11),(-1,-1),criteria)
         objpoints.append(objp)
         imgpoints.append(corners)
         # 将角点在图像上显示
         cv2.drawChessboardCorners(img, (w,h), corners, ret)
         cv2.namedWindow('findCorners', cv2.WINDOW_NORMAL)
         cv2.resizeWindow('findCorners', 810, 405)
         cv2.imshow('findCorners',img)
         cv2.waitKey(1)
 cv2.destroyAllWindows()
 #%% 标定
 ret, mtx, dist, rvecs, tvecs = \
     cv2.calibrateCamera(objpoints, imgpoints, gray.shape[::-1], None, None)

 print("ret:",ret  )
 print("mtx:\n",mtx)      # 内参数矩阵
 print("dist:\n",dist   )   # 畸变系数   distortion cofficients = (k_1,k_2,p_1,p_2,k_3)
 print("rvecs:\n",rvecs)   # 旋转向量  # 外参数
 print("tvecs:\n",tvecs  )  # 平移向量  # 外参数

标定结果里对aruco有用的是 mtx 和 dist。

然后打印包含aruco的marker的纸，运行下面的代码就可以玩了：

 import numpy as np
 import time
 import cv2
 import cv2.aruco as aruco  

 #with np.load('webcam_calibration_output.npz') as X:
 #    mtx, dist, _, _ = [X[i] for i in ('mtx','dist','rvecs','tvecs')]

 #mtx =
 #2946.48    0    1980.53
 #0    2945.41    1129.25
 #0    0    1

 mtx = np.array([
         [2946.48,       0, 1980.53],
         [      0, 2945.41, 1129.25],
         [      0,       0,       1],
         ])
 #我的手机拍棋盘的时候图片大小是 4000 x 2250
 #ip摄像头拍视频的时候设置的是 1920 x 1080，长宽比是一样的，
 #ip摄像头设置分辨率的时候注意一下

 dist = np.array( [0.226317, -1.21478, 0.00170689, -0.000334551, 1.9892] )

 video = "http://admin:admin@192.168.1.2:8081/"   # 手机ip摄像头
 # 根据ip摄像头在你手机上生成的ip地址更改，右上角可修改图像分辨率

 cap = cv2.VideoCapture(video)

 font = cv2.FONT_HERSHEY_SIMPLEX #font for displaying text (below)  

 #num = 0
 while True:
     ret, frame = cap.read()
     # operations on the frame come here  

     gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
     aruco_dict = aruco.Dictionary_get(aruco.DICT_6X6_250)
     parameters =  aruco.DetectorParameters_create()  

     '''
     detectMarkers(...)
         detectMarkers(image, dictionary[, corners[, ids[, parameters[, rejectedI
         mgPoints]]]]) -> corners, ids, rejectedImgPoints
     '''  

     #lists of ids and the corners beloning to each id
     corners, ids, rejectedImgPoints = aruco.detectMarkers(gray,
                                                           aruco_dict,
                                                           parameters=parameters)  

 #    if ids != None:
     if ids is not None:

         rvec, tvec, _ = aruco.estimatePoseSingleMarkers(corners, 0.05, mtx, dist)
         # Estimate pose of each marker and return the values rvet and tvec---different
         # from camera coeficcients
         (rvec-tvec).any() # get rid of that nasty numpy value array error  

 #        aruco.drawAxis(frame, mtx, dist, rvec, tvec, 0.1) #Draw Axis
 #        aruco.drawDetectedMarkers(frame, corners) #Draw A square around the markers

         for i in range(rvec.shape[0]):
             aruco.drawAxis(frame, mtx, dist, rvec[i, :, :], tvec[i, :, :], 0.03)
             aruco.drawDetectedMarkers(frame, corners)
         ###### DRAW ID #####
 #        cv2.putText(frame, "Id: " + str(ids), (0,64), font, 1, (0,255,0),2,cv2.LINE_AA)  

     else:
         ##### DRAW "NO IDS" #####
         cv2.putText(frame, "No Ids", (0,64), font, 1, (0,255,0),2,cv2.LINE_AA)  

     # Display the resulting frame
     cv2.imshow("frame",frame)  

     key = cv2.waitKey(1)

     if key == 27:         # 按esc键退出
         print('esc break...')
         cap.release()
         cv2.destroyAllWindows()
         break

     if key == ord(' '):   # 按空格键保存
 #        num = num + 1
 #        filename = "frames_%s.jpg" % num  # 保存一张图像
         filename = str(time.time())[:10] + ".jpg"
         cv2.imwrite(filename, frame)

最后效果如下：