如何将 k4a_image_t 转换为 opencv 矩阵？ （Azure Kinect 传感器 SDK）

Question

我开始尝试使用 Azure Kinect 传感器 SDK。我经历了 official how-to guides。我可以从传感器捕获图像作为原始缓冲区，但我想将它们转换为 opencv 矩阵。

Answer 1

首先，您需要告诉 Azure Kinect 传感器以 BGRA32 格式捕获彩色图像（而不是 JPEG 或其他压缩格式）。 深度图像以 16 位 1 通道格式捕获。

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您可以通过设置配置来做到这一点：

k4a_device_configuration_t config = K4A_DEVICE_CONFIG_INIT_DISABLE_ALL;
config.camera_fps = K4A_FRAMES_PER_SECOND_30;
config.color_format = K4A_IMAGE_FORMAT_COLOR_BGRA32; // <==== For Color image
config.color_resolution = K4A_COLOR_RESOLUTION_2160P;
config.depth_mode = K4A_DEPTH_MODE_NFOV_UNBINNED; // <==== For Depth image 

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然后，配置完成后，您可以通过以下方式捕获彩色图像，然后使用原始缓冲区从彩色图像创建一个 opencv 矩阵：

k4a_image_t colorImage = k4a_capture_get_color_image(capture); // get image metadata
if (colorImage != NULL)
{
    // you can check the format with this function
    k4a_image_format_t format = k4a_image_get_format(colorImage); // K4A_IMAGE_FORMAT_COLOR_BGRA32 

    // get raw buffer
    uint8_t* buffer = k4a_image_get_buffer(colorImage);

    // convert the raw buffer to cv::Mat
    int rows = k4a_image_get_height_pixels(colorImage);
    int cols = k4a_image_get_width_pixels(colorImage);
    cv::Mat colorMat(rows , cols, CV_8UC4, (void*)buffer, cv::Mat::AUTO_STEP);

    // ...

    k4a_image_release(colorImage);
}

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同样，对于深度图，你可以像这样将原始深度数据转换为opencv（注意，矩阵类型已经改变！）：

k4a_image_t depthImage = k4a_capture_get_depth_image(capture); // get image metadata
if (depthImage != NULL)
{
    // you can check the format with this function
    k4a_image_format_t format = k4a_image_get_format(depthImage); // K4A_IMAGE_FORMAT_DEPTH16 

    // get raw buffer
    uint8_t* buffer = k4a_image_get_buffer(depthImage);

    // convert the raw buffer to cv::Mat
    int rows = k4a_image_get_height_pixels(depthImage);
    int cols = k4a_image_get_width_pixels(depthImage);
    cv::Mat depthMat(rows, cols, CV_16U, (void*)buffer, cv::Mat::AUTO_STEP);

    // ...

    k4a_image_release(depthImage);
}

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NOTE: Opencv matrix constructor will not copy or allocate new memory for the pointer, instead it initializes the matrix head to point to the specified data!

---

Sources:

• Azure Kinect Sensor SDK - k4a_image_format_t
• Azure Kinect Sensor SDK - k4a_image_t
• Opencv Mat

Answer 2

#pragma comment(lib, "k4a.lib")
#include <k4a/k4a.h>

#include <opencv4/opencv2/opencv.hpp>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>

using namespace std;

using namespace cv;

int main()
{
    // getting the capture
    k4a_capture_t capture;

    const int32_t TIMEOUT_IN_MS = 1000;


    uint32_t count = k4a_device_get_installed_count();
    if (count == 0)
    {
        printf("No k4a devices attached!\n");
        return 1;
    }

    // Open the first plugged in Kinect device
    k4a_device_t device = NULL;
    if (K4A_FAILED(k4a_device_open(K4A_DEVICE_DEFAULT, &device)))
    {
        printf("Failed to open k4a device!\n");
        return 1;
    }

    // Get the size of the serial number
    size_t serial_size = 0;
    k4a_device_get_serialnum(device, NULL, &serial_size);

    // Allocate memory for the serial, then acquire it
    char *serial = (char*)(malloc(serial_size));
    k4a_device_get_serialnum(device, serial, &serial_size);
    printf("Opened device: %s\n", serial);
    free(serial);

    // Configure a stream of 4096x3072 BRGA color data at 15 frames per second
    k4a_device_configuration_t config = K4A_DEVICE_CONFIG_INIT_DISABLE_ALL;
    config.camera_fps       = K4A_FRAMES_PER_SECOND_30;
    config.color_format     = K4A_IMAGE_FORMAT_COLOR_BGRA32;
    config.color_resolution = K4A_COLOR_RESOLUTION_1080P;
    config.depth_mode = K4A_DEPTH_MODE_NFOV_UNBINNED;
    config.synchronized_images_only = true;

    // Start the camera with the given configuration
    k4a_device_start_cameras(device, &config);

    int frame_count = 0;

    k4a_device_get_capture(device, &capture, TIMEOUT_IN_MS);
    k4a_image_t color_image = k4a_capture_get_color_image(capture);

    uint8_t* color_buffer = k4a_image_get_buffer(color_image);

    int rows = k4a_image_get_height_pixels(color_image);
    int cols = k4a_image_get_width_pixels(color_image);

    cv::Mat color(rows, cols, CV_8UC4, (void*)color_buffer, cv::Mat::AUTO_STEP);

    //cv::imshow("random", color);

    k4a_image_t depth_image = k4a_capture_get_depth_image(capture);

    uint8_t* depth_buffer = k4a_image_get_buffer(depth_image);

    int depth_rows = k4a_image_get_height_pixels(depth_image);
    int depth_cols = k4a_image_get_width_pixels(depth_image);

    cv::Mat depth(depth_rows, depth_cols, CV_8UC4, (void*)depth_buffer, cv::Mat::AUTO_STEP);
    //cv::imshow("depth image",depth);
    //cv::waitKey(0);

    cv::imwrite("depth.jpg",depth);
    cv::imwrite("color.jpg",color);

    k4a_device_stop_cameras(device);
    k4a_device_close(device);
    return 0;
}

使用 cmake 完成构建：https://github.com/ShitalAdhikari/Azure_kinect