OpenCV

Calibration

//

distortion = np.loadtxt("畸变系数txt文件")
intrinsic_matrix = np.loadtxt("内参矩阵")
# 消除图像distortion
img = cv2.undistort(img, intrinsic_matrix, distortion)

# 消除图像点的畸变（如果没有指定P，那么将输出归一化坐标点）
img = cv2.undistortPoints(src=points, cameraMatrix=self.intri_matrix, distCoeffs=distortion, P=intrinsic_matrix)

Q&A

Q1：为什么 projectPoints 含有畸变系数？

A1：其得到的是考虑了畸变的二维图像点

在计算重投影误差时，由于真值考虑上了畸变模型（opencv检测到的棋盘格2D点），则三维的投影点也需要考虑上畸变模型。

# 使用OpenCV 3D->2D的接口的话需要去一次畸变才是自己写的重投影
re_projection, _ = cv2.projectPoints(corners_world[:, :3].astype(np.float32), rvec, tvec, self.intri_matrix, self.distor)
undistor_img_cv = cv2.undistortPoints(src=np.squeeze(re_projection), cameraMatrix=self.intri_matrix,
                                                  distCoeffs=self.distor,
                                                  P=self.intri_matrix)

undistor_img_ours, _ = self.lidar_to_img(corners_world[:, :3])

Camera

打开笔记本内置相机

// TODO

import cv2

capture = cv2.VideoCapture(0)

# VideoCaptureProperties
capture.set(3, 1280)  # width
capture.set(4, 720)  # height
capture.set(5, 30)  # frame rate
cv2.namedWindow('frame', 0)
while True:
   ret, frame = capture.read()
   cv2.imshow('frame', frame)
   # return the Unicode code point for a one-character string.
   if cv2.waitKey(1) == ord('q'):
      break
cv2.destroyWindow('frame')

Element

//

# 一、给定中心位置和半径画实心或空心圆
img = cv2.imread("图形路径")
cv2.circle(img, center=(500, 400), radius=100, color=(0, 0, 255), thickness=2)

# e.g. 可视化2D的投影点云
for (x, y), c in zip(pts_2d, color):
   # 图片，圆心位置位置，圆半径，圆颜色，边界厚度（-1：填充）
   cv2.circle(img, (x, y), 1, [c[2], c[1], c[0]], -1)

# 二、添加文本
cv2.putText(img, "文本", <对应位置>, cv2.FONT_HERSHEY_SIMPLEX,
                  fontHeight=0.5, color(255, 0, 255), thickness=1)

# 三、交互画ROI
ROI = cv2.selectROIs(img, fromCenter=False, showCrosshair=True)

Geometry

#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>

// 判断点是否在某个闭合轮廓中
// region need float
std::vector<cv::Point2f> region = {{452, 385}, {830, 385}, {393, 540}, {900, 540}};
cv::Point2d bottom_middle_point = {452, 399};
int ret = cv::pointPolygonTest(region, point, false);

# 判断点是否在某个闭合轮廓中
# It returns positive (inside), negative (outside), or zero (on an edge) value
# False: 不返回具体的距离仅返回（-1，0，1）
sign = cv2.pointPolygonTest(contour, point, False)

Image

// 读取图片
std::string file_name = "";
cv::imread(file_name);

import cv2

# 显示图片
cv2.imshow("窗口名称", cv2.resize(img, dsize=(600, 320)))

# 图层叠放（参数：加权系数、偏置项）
add_img =  cv2.addWeighted(img_1, 0.7, img_2, 0.3, 0)

# 图片拼接
image = cv2.hconcat([image_l, image_r])

# 颜色通道变换
cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# 伪彩色
img = cv2.imread("文件名", cv2.IMREAD_GRAYSCALE)
img = cv2.applyColorMap(img, cv2.COLORMAP_JET)

Key

//

key = cv2.waitKey(1) # unit: ms
if key & 0xFF == ord('q'):
   break

Mat

// Point2f -> Point2d
std::vector<cv::Point2f> vector1;
std::vector<cv::Point2d> vector2;
for (auto & point : vector1) {
   vector2.push_back(cv::Point2d((int) point.x, (int) point.y));
}

# TODO

Smooth

# 一、腐蚀操作
def dilate(img):
    kernel = np.ones((3, 3), dtype=np.uint8)
    img = cv2.dilate(img, kernel, iterations=3)
    return img

# 二、高斯滤波
img = cv2.GaussianBlur(img, (5, 5), 0, 0, cv2.BORDER_DEFAULT)

Window

//

# 定义窗口名称
cv2.namedWindow("窗口名称")

// 销毁窗口
cv2.destroyWindow('frame')
cv2.destroyAllWindows()

Q&A

Q1：xkbcommon: ERROR: failed to add default include path .../anaconda3/envs/.../share/X11/xkb

A1：添加环境变量 XKB_CONFIG_ROOT=/usr/share/X11/xkb

Q2&A2：qt.qpa.plugin:Could not load the Qt platform plugin “xcb“