[...]
There is no builtin .NET code to do zooming, but it can be
accomplished by setting the Top and Left properties of the picturebox
to be outside of the form.
I think I would call that "panning".
The PictureBox does offer some minimal control over basic zooming
behavior. For anything more complicated than that, a custom control would
be required. Based on what little I know about WPF, using WPF is probably
the easiest way. But it wouldn't be hard to write a custom control that
handles it either.
Drawing oneself, you would presumably be using the Graphics.DrawImage()
method to draw the bitmap on the screen, in the form. To scale (zoom)
and/or offset (pan) the drawing, you can simply provide destination
dimensions for the image that are different from the source dimensions
(zoom in, dimensions are larger, zoom out, smaller...pan down and/or
right, origin of destination is to the left or up from the visible origin
in the control, and vice a versa). Alternatively, one can modify the
effective viewport being used to draw by creating a new transformation
matrix and assigning it to the Transform property of the Graphics instance
being used to draw.
Of course, you also need to provide a UI to control zoom and pan. That's
an entirely separate matter. But a standard click-and-drag or
scrollbar-based UI is fairly straightforward.
Pete
