A Pixel Is Not A Little Square

http://alvyray.com/Memos/CG/Microsoft/6_pixel.pdf
https://news.ycombinator.com/item?id=43769959

A pixel is a point sample. It exists only at a point. For a color picture, a pixel might actually contain three samples, one for each primary color contributing to the picture at the sampling point. We can still think of this as a point sample of a color. But we cannot think of a pixel as a square—or anything other than a point.