I had some of the same frustration with Python, and eventually switched to julia-lang for this kind of stuff. You still don't get the static type analysis step of something like C++ or Haskell, but you can more easily control the types that flow through your computations (compared to python) by using julia's type system. You don't have to deal with numpy's magic, because julia has very nice linear algebra built-ins, and as long as you produce type-stable julia code it's usually plenty fast. There's also an opencv package for julia, although I've never used it.