If you’re like me then sometimes when you are look at an XKCD cartoon you wonder where the horizontal center axis of the cartoon is. For example, some strips are drawn in such a way that what appears to be the middle is not actually the middle.

The trick to finding the middle is to realize that the button “Random” is centered in the column and that the downward stroke of the letter D is the center of that button. Therefore just visually follow the downward stroke of the D in Random and that is the center of the strip. Here’s an example:

I don’t yet know a trick for finding the visual center of an image but I’ve never really felt compelled to do so, and I could always use a screen ruler if I did.