[kalal]

This is important point indeed. Here is what helps myself, when thinking about pixels.

- pixels are point samples in 2D space - their position is exact - position of of top-left point is (0,0) - position of bottom right is (cols-1,rows-1)

This way all math work (subsampling, affine or perspective warps, lens distortion, or even warping between image and any layer neural network). Failure to do that, will cause subtle issues that will degrade your performance. These will become quite important when working with pixel accurate methods (3d object tracking, object detection in tiny resolutions and 1-1 mapping between OpenGL and Neural Network). So I have to agree, pixels are not tiny squares, they are dots in 2d space.