Azure Kinect获取相机内参

在采集点云数据时需要根据相机不同depth、color分辨率调整对应相机内参u0(px)、v0(py)、fx、fy，那么具体内参怎么获得呢？就跟随ludaner一起来看看吧。

其实Azure-Kinect-Sensor-SDK已经提供了example代码，只需编译运行即可:Azure-Kinect-Sensor-SDK/main.cpp at develop · microsoft/Azure-Kinect-Sensor-SDK · GitHubA cross platform (Linux and Windows) user mode SDK to read data from your Azure Kinect device. - Azure-Kinect-Sensor-SDK/main.cpp at develop · microsoft/Azure-Kinect-Sensor-SDKhttps://github.com/microsoft/Azure-Kinect-Sensor-SDK/blob/develop/examples/calibration/main.cpp

顺便把main.cpp代码贴出来

#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
#include <vector>
#include <k4a/k4a.h>
using namespace std;

static string get_serial(k4a_device_t device)
{
    size_t serial_number_length = 0;

    if (K4A_BUFFER_RESULT_TOO_SMALL != k4a_device_get_serialnum(device, NULL, &serial_number_length))
    {
        cout << "Failed to get serial number length" << endl;
        k4a_device_close(device);
        exit(-1);
    }

    char *serial_number = new (std::nothrow) char[serial_number_length];
    if (serial_number == NULL)
    {
        cout << "Failed to allocate memory for serial number (" << serial_number_length << " bytes)" << endl;
        k4a_device_close(device);
        exit(-1);
    }

    if (K4A_BUFFER_RESULT_SUCCEEDED != k4a_device_get_serialnum(device, serial_number, &serial_number_length))
    {
        cout << "Failed to get serial number" << endl;
        delete[] serial_number;
        serial_number = NULL;
        k4a_device_close(device);
        exit(-1);
    }

    string s(serial_number);
    delete[] serial_number;
    serial_number = NULL;
    return s;
}

static void print_calibration()
{
    uint32_t device_count = k4a_device_get_installed_count();
    cout << "Found " << device_count << " connected devices:" << endl;
    cout << fixed << setprecision(6);

    for (uint8_t deviceIndex = 0; deviceIndex < device_count; deviceIndex++)
    {
        k4a_device_t device = NULL;
        if (K4A_RESULT_SUCCEEDED != k4a_device_open(deviceIndex, &device))
        {
            cout << deviceIndex << ": Failed to open device" << endl;
            exit(-1);
        }

        k4a_calibration_t calibration;

        k4a_device_configuration_t deviceConfig = K4A_DEVICE_CONFIG_INIT_DISABLE_ALL;
        deviceConfig.color_format = K4A_IMAGE_FORMAT_COLOR_MJPG;
        deviceConfig.color_resolution = K4A_COLOR_RESOLUTION_1080P;
        deviceConfig.depth_mode = K4A_DEPTH_MODE_NFOV_UNBINNED;
        deviceConfig.camera_fps = K4A_FRAMES_PER_SECOND_30;
        deviceConfig.wired_sync_mode = K4A_WIRED_SYNC_MODE_STANDALONE;
        deviceConfig.synchronized_images_only = true;

        // get calibration
        if (K4A_RESULT_SUCCEEDED !=
            k4a_device_get_calibration(device, deviceConfig.depth_mode, deviceConfig.color_resolution, &calibration))
        {
            cout << "Failed to get calibration" << endl;
            exit(-1);
        }

        auto calib = calibration.depth_camera_calibration;

        cout << "
===== Device " << (int)deviceIndex << ": " << get_serial(device) << " =====
";
        cout << "resolution width: " << calib.resolution_width << endl;
        cout << "resolution height: " << calib.resolution_height << endl;
        cout << "principal point x: " << calib.intrinsics.parameters.param.cx << endl;
        cout << "principal point y: " << calib.intrinsics.parameters.param.cy << endl;
        cout << "focal length x: " << calib.intrinsics.parameters.param.fx << endl;
        cout << "focal length y: " << calib.intrinsics.parameters.param.fy << endl;
        cout << "radial distortion coefficients:" << endl;
        cout << "k1: " << calib.intrinsics.parameters.param.k1 << endl;
        cout << "k2: " << calib.intrinsics.parameters.param.k2 << endl;
        cout << "k3: " << calib.intrinsics.parameters.param.k3 << endl;
        cout << "k4: " << calib.intrinsics.parameters.param.k4 << endl;
        cout << "k5: " << calib.intrinsics.parameters.param.k5 << endl;
        cout << "k6: " << calib.intrinsics.parameters.param.k6 << endl;
        cout << "center of distortion in Z=1 plane, x: " << calib.intrinsics.parameters.param.codx << endl;
        cout << "center of distortion in Z=1 plane, y: " << calib.intrinsics.parameters.param.cody << endl;
        cout << "tangential distortion coefficient x: " << calib.intrinsics.parameters.param.p1 << endl;
        cout << "tangential distortion coefficient y: " << calib.intrinsics.parameters.param.p2 << endl;
        cout << "metric radius: " << calib.intrinsics.parameters.param.metric_radius << endl;

        k4a_device_close(device);
    }
}

static void calibration_blob(uint8_t deviceIndex = 0, string filename = "calibration.json")
{
    k4a_device_t device = NULL;

    if (K4A_RESULT_SUCCEEDED != k4a_device_open(deviceIndex, &device))
    {
        cout << deviceIndex << ": Failed to open device" << endl;
        exit(-1);
    }

    size_t calibration_size = 0;
    k4a_buffer_result_t buffer_result = k4a_device_get_raw_calibration(device, NULL, &calibration_size);
    if (buffer_result == K4A_BUFFER_RESULT_TOO_SMALL)
    {
        vector<uint8_t> calibration_buffer = vector<uint8_t>(calibration_size);
        buffer_result = k4a_device_get_raw_calibration(device, calibration_buffer.data(), &calibration_size);
        if (buffer_result == K4A_BUFFER_RESULT_SUCCEEDED)
        {
            ofstream file(filename, ofstream::binary);
            file.write(reinterpret_cast<const char *>(&calibration_buffer[0]), (long)calibration_size);
            file.close();
            cout << "Calibration blob for device " << (int)deviceIndex << " (serial no. " << get_serial(device)
                 << ") is saved to " << filename << endl;
        }
        else
        {
            cout << "Failed to get calibration blob" << endl;
            exit(-1);
        }
    }
    else
    {
        cout << "Failed to get calibration blob size" << endl;
        exit(-1);
    }
}

static void print_usage()
{
    cout << "Usage: calibration_info [device_id] [output_file]" << endl;
    cout << "Using calibration_info.exe without any command line arguments will display" << endl
         << "calibration info of all connected devices in stdout. If a device_id is given" << endl
         << "(0 for default device), the calibration.json file of that device will be" << endl
         << "saved to the current directory." << endl;
}

int main(int argc, char **argv)
{
    if (argc == 1)
    {
        print_calibration();
    }
    else if (argc == 2)
    {
        calibration_blob((uint8_t)atoi(argv[1]), "calibration.json");
    }
    else if (argc == 3)
    {
        calibration_blob((uint8_t)atoi(argv[1]), argv[2]);
    }
    else
    {
        print_usage();
    }

    return 0;
}

cmake编译不通过的添加或修改CMakeLists.txt为

## k4a
find_package(k4a 1.3.0 QUIET)
include_directories(${K4A_INCLUDE_DIRS})

add_executable(calibration_info main.cpp)
target_link_libraries(calibration_info PRIVATE k4a::k4a)

编译成功运行，可指定直接print输出或输出为json文件

修改以下代码输出不同分辨率：

deviceConfig.color_resolution = K4A_COLOR_RESOLUTION_1536P;
deviceConfig.depth_mode = K4A_DEPTH_MODE_WFOV_UNBINNED;

Azure Kinect提供的所有分辨率可在以下网页查看https://docs.microsoft.com/zh-cn/azure/Kinect-dk/hardware-specification

修改以下代码可选择输出color或depth相机分辨率

// color_camera_calibration, depth_camera_calibration
auto calib = calibration.color_camera_calibration; 

运行程序即可，po一个结果

Found 1 connected devices:

===== Device 0:  =====
resolution width: 2048
resolution height: 1536
principal point x: 1023.543701
principal point y: 777.486084
focal length x: 975.207458
focal length y: 974.770630
radial distortion coefficients:
k1: 0.205187
k2: -2.718986
k3: 1.783927
k4: 0.082789
k5: -2.509135
k6: 1.684085
center of distortion in Z=1 plane, x: 0.000000
center of distortion in Z=1 plane, y: 0.000000
tangential distortion coefficient x: 0.000927
tangential distortion coefficient y: -0.000091
metric radius: 0.000000

参考资料

​​​​​​​[1]https://github.com/microsoft/Azure-Kinect-Sensor-SDK/issues/1282#issuecomment-657684355