Convert grayscale to rgb c++

To convert a grayscale image to an RGB image in C++, you can use the OpenCV library. Here is an example code snippet:

#include <opencv2/opencv.hpp>

using namespace cv;

int main()
{
    // Load the grayscale image
    Mat gray_img = imread("grayscale_image.jpg", IMREAD_GRAYSCALE);

    // Create a new RGB image
    Mat rgb_img;
    cvtColor(gray_img, rgb_img, COLOR_GRAY2RGB);

    // Save the new RGB image
    imwrite("rgb_image.jpg", rgb_img);

    return 0;
}

In this example, we first load the grayscale image using the `imread()` function with the flag `IMREAD_GRAYSCALE`. Then, we create a new RGB image by converting the grayscale image to RGB using the `cvtColor()` function with the flag `COLOR_GRAY2RGB`. Finally, we save the new RGB image using the `imwrite()` function.