Regions in GDI+

A region is a portion of the display area of an output device. You can construct a region from a rectangle or a path. You can also create complex regions by combining existing regions.

The following illustration shows two regions: one constructed from a rectangle, and the other constructed from an ellipse.

 

The Region class provides the following methods for combining regions: Intersect , Union , Xor , Exclude , and Complement.

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Intersection

The intersection of two regions is the set of all points belonging to both regions. The following illustration shows the intersection (violet color).

 

The following code example shows how to draw the intersection of two regions:

'create region object Dim myRegion As New Region(myRectangle) 'intersect two region myRegion.Intersect(myPath) 'draw the intersection myGraphics.FillRegion(Brushes.BlueViolet, myRegion) 

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Union

The union is the set of all points belonging to one or the other or both regions. The following illustration shows the union.

 

The following code example demonstrates how to draw the union of two regions:

'create region object Dim myRegion As New Region(myRectangle) 'union two region myRegion.Union(myPath) 'draw the union myGraphics.FillRegion(Brushes.BlueViolet, myRegion) 

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Complement

The complement of a region is the set of all points that are not in the region. The following illustration shows the complement (violet color).

 

The following code example demonstrates how to draw the complement of a region:

'create region object Dim myRegion As New Region(myRectangle) 'set the complement of a region myRegion.Complement(myPath) 'draw the complement myGraphics.FillRegion(Brushes.BlueViolet, myRegion) 

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Xor

Xor is a process to produce a region that contains all points that belong to one region or the other, but not both. The following illustration show the Xor region (violet color).

 

The following code example demonstrates how to draw the Xor of region:

'create region object Dim myRegion As New Region(myRectangle) 'set the Xor of a region myRegion.Xor(myPath) 'draw the Xor myGraphics.FillRegion(Brushes.BlueViolet, myRegion) 

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Exclude

Exclude is a process to produces a region that contains all points in the first region that are not in the second region. The following illustration shows the exclude region (violet color).

 

The following code example demonstrates how to exclude a region:

'create region object Dim myRegion As New Region(myRectangle) 'create the second region Dim myRegion2 as New Region(myPath) 'exclude region myRegion.Exclude(myRegion2) 'draw the exclude region myGraphics.FillRegion(Brushes.BlueViolet, myRegion)