5.22 Screen Coordinates Screen
You can directly enter corner coordinates on this screen for use with
the passes='o' option. You can also use <F4> to reset the coordinates
to the defaults for the current fractal type.
There are two formats for the display: corners or center-mag. You can
toggle between the two by using <F7>.
In corners mode, corner coordinate values are entered directly. Usually
only the top-left and bottom-right corners need be specified - the
bottom left corner can be entered as zeros to default to an ordinary
unrotated rectangular area. For rotated or skewed images, the bottom
left corner must also be specified.
In center-mag mode the screen area is described by entering the
coordinates for the center of the rectangle, and its magnification
factor. Usually only these three values are needed, but the user can
also specify the amount that the image is stretched, rotated and skewed.