Creating cv::Mat from std::vector<float> in C++

In C++, create a cv::Mat from a vector<float> data

To create a cv::Mat from a std::vector<float> in C++, you can use the OpenCV library. The cv::Mat class is a fundamental data structure in OpenCV used to store image data, and it can be constructed from various data sources, including std::vector.

Here's a step-by-step example of how to create a cv::Mat from a std::vector<float>:

1. Include the necessary headers.
2. Define the std::vector<float> with your data.
3. Create the cv::Mat using the data from the vector.

Below is a complete example:

#include <iostream>
#include <vector>
#include <opencv2/opencv.hpp>

int main() {
    // Step 1: Include the necessary headers
    // (Already done above)

    // Step 2: Define the std::vector<float> with your data
    std::vector<float> data = {
        1.0f, 2.0f, 3.0f,
        4.0f, 5.0f, 6.0f,
        7.0f, 8.0f, 9.0f
    };

    // Step 3: Create the cv::Mat using the data from the vector
    // Define the dimensions of the matrix
    int rows = 3;
    int cols = 3;

    // Create the cv::Mat from the vector
    cv::Mat mat(rows, cols, CV_32F, data.data());

    // Print the matrix to verify
    std::cout << "Matrix created from vector<float>:" << std::endl;
    std::cout << mat << std::endl;

    return 0;
}

Explanation:

1. Include Headers: The necessary headers for using OpenCV and standard C++ libraries are included.
2. Define Vector: A std::vector<float> named data is defined and initialized with some values.
3. Create cv::Mat:
   • The dimensions of the matrix (rows and cols) are specified.
   • The cv::Mat is created using the constructor that takes the number of rows, columns, type (CV_32F for a 32-bit float), and a pointer to the data (data.data()).

Important Notes:

• The data.data() function returns a pointer to the underlying array of the vector, which is used by cv::Mat to access the data.
• The cv::Mat created this way does not copy the data; it uses the data directly from the vector. If the vector goes out of scope or is modified, the cv::Mat will be affected. If you need a deep copy, you can use the clone() method of cv::Mat.

cv::Mat matCopy = mat.clone();

This example demonstrates how to create a cv::Mat from a std::vector<float> in C++. Adjust the dimensions and data as needed for your specific use case.