
Zoom Box Commands

If the user has drawn a zoom box on the screen and presses the "d"
key (or selects "Create image" from the "Draw" menu), the program
assumes that the user wishes to zoom in on the selected area.

Moving the zoom box means moving it around on the screen without
changing its size or shape. Draw a zoom box, then press the left
mouse button down when the pointer is inside the zoom box. The outline
of the zoom box will change to a dotted line and the cursor will change
to a cross-arrow. While holding the mouse button down, move the cursor
around the screen and the outline of the zoom box will follow the mouse
pointer. When the zoom box is positioned where you want it, release the
mouse button and the outline of the zoom box will revert to a solid line.
All done. Note that if you press the mouse button down outside the zoom
box, the program assumes that you want to draw a different zoom box, and
cancels the current zoom box, and any move or stretch operation that is in
effect. Also note that if you draw a zoom box that is too small (the
minimum size is 25 x 25 pixels), the box will not be drawn. This also is
a short cut for cancelling a zoom box. Simply click the left mouse button
when the pointer is outside the zoom box and the zoom box and any pending
functions will be cancelled. If you move the zoom box so that the outside
edge of the box is outside the visible window, the area outside of
the visible window will not be included in the zoomed in or out image.

Stretching the zoom box means changing its shape. The zoom box may be
stretched vertically, horizontally, or diagonally. After drawing a
zoom box on the screen some additional lines will appear on the zoom
box. The boxes that are created by these lines are zoom box "handles".
Press the left mouse button down in one of the handles and the cursor
will change to the appropriate arrow (either up, down, left, right, or
toward one of the four corners). Hold the mouse button down and move the
cursor and the zoom box will grow and/or shrink in the desired direction.
Experiment with changing the shape in several directions to become
familiar with the stretching operation.

Selecting Pan from the Zoom menu will draw a zoom box the full size
of the screen. Moving this zoom box around on the screen will cause
the program to select the area inside the zoom box and fill the
screen with it. This effectively "pans" the image on the screen. The
portion of the visible image that has been calculated will not be
recalculated, just re-displayed. Any portion of the image that was
not visible before the pan will be calculated and displayed.

