Adding drag handles to an ImageBox to allow resizing of selection regions
The `ImageBox` control is already a versatile little control and I use it for all sorts of tasks. One of the features I recently wanted was to allow users to be able to select a source region, then adjust this as needed. The control already allows you to draw a selection region, but if you need to adjust that ... well, you can't. You can only draw a new region. This article describes how to extend the `ImageBox` to include the ability to resize the selection region. A older demonstration which shows how to drag the selection around has also been incorporated, in a more tidy fashion than the demo.
