that is all beside the point.
you need to get more specific. you need to come up with performance numbers (since that’s what you want to discuss, performance). you need to present some basis for discussion. so far it’s been “I’m worried, what if”.
you criticized some byte reordering, yet what you said in the first post (“direct”, “stream”, “memory region”, “a cycle”) sounds too… vague to be useful. I’m inclined to wonder how much meaning you see in those words. yes, obviously that reordering costs something, whenever it’s needed. that’s a tiresome point to make.
remember, we’re all autists here. we can smell bullshit and some of us don’t have the social graces to bite our tongues or to defer judgment until the evidence is overwhelming.
all day people show up (here, stack overflow, anywhere) with nothing but a cry for help, and then people like us are expected to read minds, use crystal balls, whatever, to figure out what might be the issue. we’re skilled at keyhole surgery. we won’t just hold an entire lecture presenting some topic that’s already got plenty of exposition everywhere else (books, actual lectures, …). nor do we enjoy imagining all possible questions someone could have intended to ask, and answering them all preemptively. we’d rather ask for clarification.
if you want a conversation, it can’t be about the weather or about opinions. it has to have substance. once you’ve put some meat on the table, the weather discussion happens on its own.
as for the “arduino and raspi” bit… can you visualize me facepalming? arduinos don’t do video too well. sure, game of life on a dot matrix display, but not video. and raspis… hm well, moderately powerful CPU, and the GPU has been near unusable for a long time (thanks, drivers!). even today you can’t use OpenCL for any acceleration on that thing.
what I mean to say: “raspberry pi is slow” is obvious and allows no conclusion about OpenCV’s suitability for whatever you’re trying to do.
you hinted at “art installations”. OpenCV is for computer vision. it’s not OpenGL, it’s not made for drawing things. it’s not a GUI library either. it’s not a lot of things, but it comes with a bunch of rudimentary convenience facilities. nobody’s gonna stop you if you want to use OpenCV, for intended or unintended purposes.
but if you show up with criticism, expect to argue your own position before you ask anyone else to argue their position.