Improving performance of Imshow with OpenGL - c++

Question

I have a raspberry pi running an opencv c++ application I developed. I'm doing some image manipulation of a cv::Mat from a camera, then I resize (if needed), create a border, then display it fullscreen with cv::imshow. Right now everything works, but performance is usually limited to 8 fps at 800x480 resolution.
What I would like to do is utilize opengl to increase perofrmance. I already have opencv compiled with opengl support and can open cv::namedWindow with the cv::WINDOW_OPENGL flag, but performance is actually worse. I believe the reason is because I am still using cv::imshow with a cv::Mat and not a ogl::buffer or other data type that takes advantage of the opengl support.
So the question I have is how can I convert my cv::Mat to an ogl:buffer, or other data type (ogl::Texture2D?), and can that step be combined with some of my others (specifically cv::Mat's copyTo() )? I'm thinking instead of copying my cv::Mat to a larger cv::Mat to create the border I could go directly to a ogl::buffer for the same effect. Is that possible?
Current code, let's assume 'image' is always a 640x480 cv::Mat*:
//Create initial cv::Mat's
cv::Mat imagetemp{ cv::Mat(480, 640, image->type(), cv::Scalar(0)) };
cv::Mat borderedimage{ cv::Mat(480, 800, image->type(), cv::Scalar(0)) };
//Create fullscreen opengl window
cv::namedWindow( "Output", cv::WINDOW_OPENGL );
cv::setWindowProperty( "Output", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN );
//Loop
while( true ) {
//Get latest image
displaymutex->lock();
imagetemp = *image;
displaymutex->unlock();
//Format
imagetemp.copyTo( borderedimage.rowRange(0, 480).colRange(80, 720) );
//Display
cv::imshow( "Output", borderedimage );
cv::waitKey( 1 );
}
OK, the following code works for converting a cv::Mat to a cv::ogl::buffer, and I also simplified it a bit by using copyMakeBorder(), however the result is only 1-2 fps!! Is this just not an application that can benefit from openGL? Any other suggestions for performance improvements with or without openGL utilization?
//Create temporary cv::Mat
cv::Mat imagetemp{ cv::Mat(480, 640, image->type(), cv::Scalar(0)) };
//Create fullscreen opengl window
cv::namedWindow( "Output", cv::WINDOW_OPENGL );
cv::setWindowProperty( "Output", CV_WND_PROP_FULLSCREEN, CV_WINDOW_FULLSCREEN );
//Loop
while( true ) {
//Get latest image
displaymutex->lock();
cv::copyMakeBorder( *image,
imagetemp,
0,
0,
80,
80,
cv::BORDER_CONSTANT,
cv::Scalar(0) );
displaymutex->unlock();
//Display
buffer.copyFrom(imagetemp, cv::ogl::Buffer::ARRAY_BUFFER, true);
cv::imshow( "Output", buffer );
cv::waitKey( 1 );
}
Thanks