How to convert SFML image to OpenCV Mat in c++?

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Below code is used to convert an OpenCV Mat image into SFML image. How to convert SFML image back to Mat image?

 cv::Mat frameBGR, frameBGRA;   
 sf::Image image;    
 cv::cvtColor(frameBGR,frameRGBA,
 cv::COLOR_BGR2RGBA);    
 image.create(frameRGBA.cols,
 frameRGBA.rows, frameRGBA.ptr());

If texture or sprite can't be converted to OpenCV Mat,then is it possible to convert sf::Image to OpenGL and convert it back to cv::Mat

    sf::Texture texture;
    sf::Event event;
    sf::Sprite sprite;
    texture.loadFromImage(image);
    sprite.setTexture(texture);

Update: I referred this post, but still was not able to convert.

    void* buffer = ℑ 
    cv::Mat image_mat = cv::Mat(cvSize(500, 500),CV_8UC4, buffer, cv::Mat::AUTO_STEP);  
    cvtColor(image_mat, converted,CV_RGBA2BGR);

It crashes at below line of code (when i display image )

imshow("img", converted);