C# Regions

A Region describes the interior of a part of a form defined by a rectangle or the union of rectangles (or some other possibilities such as polygons).

The Region class is in the System.Drawing namespace.

Constructors (not all of them)

• public Region()

  Basic constructor

• public Region(Rectangle R)

  This region is the interior of R.

Methods (a few of them)

• public void Union(Region Reg)

  This expands the current Region instance to its union with Reg.

• public void Union(Rectangle R)

  This expands the current Region instance to include the interior of R.

• public void Intersect(Region Reg)

  This shrinks the current Region instance to its intersection with Reg.

• public void Intersect(Rectangle R)

  This shrinks the current Region instance to its intersection with the interior of R.

• public bool IsVisible(float X, float Y)

  This returns true if the point (X, Y) is in the Region.

Note: There is a large collection of variations on IsVisible, to check on whether any part of given rectangle is inside the Region.