title: Can I calculate NDVI with openCV C++ from an image captured from camera with IR filter
body: <p>I have an image captured by the camera with IR filter, I want to get NDVI index from that image with openCV, but I don't know how to do it, can somebody help me?
  I know the function NDVI = (NIR-R)/(NIR+R) but I can't figured out how to get NIR values from that image.</p>