Pixel centers at (0.5, 0.5) is the convention adopted by all major graphics APIs (OpenGL, DirectX, Vulkan, Metal). That’s because it makes the math, especially around image scaling, becomes a lot simpler. - HN

One common mistake is to not think in floating point coordinates all the way through. E.g. a rectangle that covers a single pixel should have coordinates like (100.0,100.0)-(101.0,101.0), NOT involving a 0.5 offset. You almost never offset anything by 0.5 in this convention. 1 pixel wide lines are an exception, but only because then the edges of the line are exactly at pixel boundaries.

• The Center of the Pixel is (0.5,0.5)