### Description
This example illustrates the Rectilinear Wipe widget. This widget is
useful for comparing two images. There are 7 different image
comparison modes.  A rectilinear wipe is a 2x2 checkerboard pattern
created by combining two separate images, where various combinations
of the checker squares are possible. Using this widget, the user can
adjust the layout of the checker pattern, such as moving the center
point, moving the horizontal separator, or moving the vertical
separator.

Pressing keys 0-6 select the various wipe modes.

For an alternative image comparison widget try the [Checkerboard widget](CheckerboardWidget). 
