使用OpenCV/python进行双目测距

时间 2019-12-08

原文原文链接

在作SLAM时，但愿用到深度图来辅助生成场景，因此要构创建体视觉，在这里使用OpenCV的Stereo库和python来进行双目立体视觉的图像处理。python

立体标定
应用标定数据
转换成深度图

标定

在开始以前，须要准备的固然是两个摄相头，根据你的需求将两个摄像头进行相对位置的固定，我是按平行来进行固定的（若是为了追求两个双目图像更高的生命度，也能够将其按必定钝角固定，这样作又限制了场景深度的扩展，根据实际需求选择）算法

因为摄像头目前是咱们手动进行定位的，咱们如今还不知道两张图像与世界坐标之间的耦合关系，因此下一步要进行的是标定，用来肯定分别获取两个摄像头的内部参数，而且根据两个摄像头在同一个世界坐标下的标定参数来获取立体参数。注：不要使用OpenCV自带的自动calbration，其对棋盘的识别率极低，使用Matlab的Camera Calibration Toolbox更为有效，具体细节请看：摄像机标定和立体标定ide

同时从两个摄像头获取图片spa

import cv2
import time

AUTO = True  # 自动拍照，或手动按s键拍照
INTERVAL = 2 # 自动拍照间隔

cv2.namedWindow("left")
cv2.namedWindow("right")
cv2.moveWindow("left", 0, 0)
cv2.moveWindow("right", 400, 0)
left_camera = cv2.VideoCapture(0)
right_camera = cv2.VideoCapture(1)

counter = 0
utc = time.time()
pattern = (12, 8) # 棋盘格尺寸
folder = "./snapshot/" # 拍照文件目录

def shot(pos, frame):
    global counter
    path = folder + pos + "_" + str(counter) + ".jpg"

    cv2.imwrite(path, frame)
    print("snapshot saved into: " + path)

while True:
    ret, left_frame = left_camera.read()
    ret, right_frame = right_camera.read()

    cv2.imshow("left", left_frame)
    cv2.imshow("right", right_frame)

    now = time.time()
    if AUTO and now - utc >= INTERVAL:
        shot("left", left_frame)
        shot("right", right_frame)
        counter += 1
        utc = now

    key = cv2.waitKey(1)
    if key == ord("q"):
        break
    elif key == ord("s"):
        shot("left", left_frame)
        shot("right", right_frame)
        counter += 1

left_camera.release()
right_camera.release()
cv2.destroyWindow("left")
cv2.destroyWindow("right")

下面是我拍摄的样本之一，能够肉眼看出来这两个摄像头成像都不是水平的，这更是须要标定的存在的意义
.net

在进行标定的过程当中，要注意的是在上面标定方法中没有提到的是，单个标定后，要对标定的数据进行错误分析（Analyse Error），如左图，是我对左摄像头的标定结果分析。图中天蓝色点明显与大部分点不聚敛，因此有多是标定时对这个图片标定出现的错误，要从新标定，在该点上点击并获取其图片名称索引，对其从新标定后，右图的结果看起来仍是比较满意的3d

在进行完立体标定后，咱们将获得以下的数据：code

Stereo calibration parameters after optimization:

Intrinsic parameters of left camera:

Focal Length:          fc_left = [ 824.93564   825.93598 ]  [ 8.21112   8.53492 ]
Principal point:       cc_left = [ 251.64723   286.58058 ]  [ 13.92642   9.11583 ]
Skew:             alpha_c_left = [ 0.00000 ]  [ 0.00000  ]   => angle of pixel axes = 90.00000  0.00000 degrees
Distortion:            kc_left = [ 0.23233   -0.99375   0.00160   0.00145  0.00000 ]  [ 0.05659   0.30408   0.00472   0.00925  0.00000 ]

Intrinsic parameters of right camera:

Focal Length:          fc_right = [ 853.66485   852.95574 ]  [ 8.76773   9.19051 ]
Principal point:       cc_right = [ 217.00856   269.37140 ]  [ 10.40940   9.47786 ]
Skew:             alpha_c_right = [ 0.00000 ]  [ 0.00000  ]   => angle of pixel axes = 90.00000  0.00000 degrees
Distortion:            kc_right = [ 0.30829   -1.61541   0.01495   -0.00758  0.00000 ]  [ 0.06567   0.55294   0.00547   0.00641  0.00000 ]

Extrinsic parameters (position of right camera wrt left camera):

Rotation vector:             om = [ 0.01911   0.03125  -0.00960 ]  [ 0.01261   0.01739  0.00112 ]
Translation vector:           T = [ -70.59612   -2.60704  18.87635 ]  [ 0.95533   0.79030  5.25024 ]

应用标定数据

咱们使用以下的代码来将其配置到python中，上面的参数都是手动填写至下面的内容中的，这样免去保存成文件再去读取，在托运填写的时候要注意数据的对应位置。orm

# filename: camera_configs.py
import cv2
import numpy as np

left_camera_matrix = np.array([[824.93564, 0., 251.64723],
                               [0., 825.93598, 286.58058],
                               [0., 0., 1.]])
left_distortion = np.array([[0.23233, -0.99375, 0.00160, 0.00145, 0.00000]])



right_camera_matrix = np.array([[853.66485, 0., 217.00856],
                                [0., 852.95574, 269.37140],
                                [0., 0., 1.]])
right_distortion = np.array([[0.30829, -1.61541, 0.01495, -0.00758, 0.00000]])

om = np.array([0.01911, 0.03125, -0.00960]) # 旋转关系向量
R = cv2.Rodrigues(om)[0]  # 使用Rodrigues变换将om变换为R
T = np.array([-70.59612, -2.60704, 18.87635]) # 平移关系向量

size = (640, 480) # 图像尺寸

# 进行立体更正
R1, R2, P1, P2, Q, validPixROI1, validPixROI2 = cv2.stereoRectify(left_camera_matrix, left_distortion,
                                                                  right_camera_matrix, right_distortion, size, R,
                                                                  T)
# 计算更正map
left_map1, left_map2 = cv2.initUndistortRectifyMap(left_camera_matrix, left_distortion, R1, P1, size, cv2.CV_16SC2)
right_map1, right_map2 = cv2.initUndistortRectifyMap(right_camera_matrix, right_distortion, R2, P2, size, cv2.CV_16SC2)

这样，咱们获得了左右摄像头的两个map，并获得了立体的Q，这些参数都将应用于下面的转换成深度图中blog

转换成深度图

import numpy as np
import cv2
import camera_configs

cv2.namedWindow("left")
cv2.namedWindow("right")
cv2.namedWindow("depth")
cv2.moveWindow("left", 0, 0)
cv2.moveWindow("right", 600, 0)
cv2.createTrackbar("num", "depth", 0, 10, lambda x: None)
cv2.createTrackbar("blockSize", "depth", 5, 255, lambda x: None)
camera1 = cv2.VideoCapture(0)
camera2 = cv2.VideoCapture(1)

# 添加点击事件，打印当前点的距离
def callbackFunc(e, x, y, f, p):
    if e == cv2.EVENT_LBUTTONDOWN:        
        print threeD[y][x]

cv2.setMouseCallback("depth", callbackFunc, None)

while True:
    ret1, frame1 = camera1.read()
    ret2, frame2 = camera2.read()

    if not ret1 or not ret2:
        break

    # 根据更正map对图片进行重构
    img1_rectified = cv2.remap(frame1, camera_configs.left_map1, camera_configs.left_map2, cv2.INTER_LINEAR)
    img2_rectified = cv2.remap(frame2, camera_configs.right_map1, camera_configs.right_map2, cv2.INTER_LINEAR)

    # 将图片置为灰度图，为StereoBM做准备
    imgL = cv2.cvtColor(img1_rectified, cv2.COLOR_BGR2GRAY)
    imgR = cv2.cvtColor(img2_rectified, cv2.COLOR_BGR2GRAY)

    # 两个trackbar用来调节不一样的参数查看效果
    num = cv2.getTrackbarPos("num", "depth")
    blockSize = cv2.getTrackbarPos("blockSize", "depth")
    if blockSize % 2 == 0:
        blockSize += 1
    if blockSize < 5:
        blockSize = 5

    # 根据Block Maching方法生成差别图（opencv里也提供了SGBM/Semi-Global Block Matching算法，有兴趣能够试试）
    stereo = cv2.StereoBM_create(numDisparities=16*num, blockSize=blockSize)
    disparity = stereo.compute(imgL, imgR)

    disp = cv2.normalize(disparity, disparity, alpha=0, beta=255, norm_type=cv2.NORM_MINMAX, dtype=cv2.CV_8U)
    # 将图片扩展至3d空间中，其z方向的值则为当前的距离
    threeD = cv2.reprojectImageTo3D(disparity.astype(np.float32)/16., camera_configs.Q)

    cv2.imshow("left", img1_rectified)
    cv2.imshow("right", img2_rectified)
    cv2.imshow("depth", disp)

    key = cv2.waitKey(1)
    if key == ord("q"):
        break
    elif key == ord("s"):
        cv2.imwrite("./snapshot/BM_left.jpg", imgL)
        cv2.imwrite("./snapshot/BM_right.jpg", imgR)
        cv2.imwrite("./snapshot/BM_depth.jpg", disp)

camera1.release()
camera2.release()
cv2.destroyAllWindows()

下面则是一附成像图，最右侧的为生成的disparity图，按照上面的代码，在图上点击则能够读取到该点的距离
索引

Have fun.