Huh. I thought it was obvious: e.g., the top-left corner of the screen is (0, 0), the bottom-right corner is (640, 480), and pixels are 1x1 — we take the coordi

Huh. I thought it was obvious: e.g., the top-left corner of the screen is (0, 0), the bottom-right corner is (640, 480), and pixels are 1x1 — we take the coordinate of their top-left corner to be their coordinate, so the top-left pixel has coordinates (0, 0), and the bottom-right one has (639, 479), and obviously the coordinates of their centres are (0.5, 0.5) and (639.5, 479.5). But apparently some people treated pixels as geometrical points without size?