I'm wondering if I could specify the size and position accurately by input the width and height and the x-y coordinates of the rectangular or ellipse selection. I want to have a very small selected region but it seems hard to obtain by moving mouse manually. As for the wanted position, I can move the selection region using the UpDownLeftRight keys.
With the rectangular and elliptical marquee tools you can specify the size by setting the
Then you can use the mouse and/or keyboard arrow keys to position the selection.