OpenCV Coordinate system for Camera Matrix Entries

Question

I'm trying to use stereoRectify. Instead of calibrating my cameras using stereoCalibrate, I already have some information which I will use to create the camera matrices, which are input to stereoRectify. The camera matrix is

/fx 0 cx\

|0 fy cy|

\0 0 1 /

where fx, fy is the focal length in pixels, and cx and cy are the principal points. I have these values. My question is whether the coordinates of cx and cy are supposed to be in pixel coordinates (where the "origin" is at the top left) or image coordinates (where the origin is at the bottom left).

Answer 1

Origin is top left. As I have seen so far working with OpenCV, image coordinates origin is always top left, why do you make this distinction between "image" and "pixel" coordinates?