Solved

Fill the area outside a Polygon (opposite of Graphics.FillPolygon)

Posted on 2009-03-31
869 Views
Last Modified: 2013-12-17
The code snippet below will draw a polygon and then fill the area inside of that polygon.  I would like to draw a polygon (an array of points) and fill the area OUTSIDE of that polygon with a color - basically blank the area outside of a polygon with a color

Thanks
``````Private Sub Form1_Paint(ByVal sender As Object, ByVal e As _

System.Windows.Forms.PaintEventArgs) Handles _

MyBase.Paint

Dim polypoints() As Point

' Draw a polygon.

polypoints = New Point() { _

New Point(20, 110), _

New Point(90, 150), _

New Point(90, 100), _

New Point(20, 150) _

}

e.Graphics.FillPolygon(Brushes.Red, polypoints)

e.Graphics.DrawPolygon(Pens.Green, polypoints)

End Sub
``````
0
Question by:tedunni
• 2
4 Comments

LVL 14

Expert Comment

ID: 24033807
Could you not just draw a box or rectangle over the entire screen and fill it with your color, then draw the polygon and fill it as white?
0

Author Comment

ID: 24033891
What I receive first is a bitmap image with colors and shapes already on it.  I also receive the polygon as an input.  I then take that bitmap and then draw a polygon on it.  At that point I want to color the area outside of the polygon.

I don't believe I can do what you are suggesting jjardine because I would lose the image data that is inside the polygon.
0

LVL 85

Accepted Solution

Mike Tomlinson earned 250 total points
ID: 24034376
Here is a simple example...
``````Imports System.Drawing.Drawing2D

Public Class Form1

Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint

Dim polypoints() As Point

' Draw a polygon.

polypoints = New Point() { _

New Point(25, 100), _

New Point(275, 350), _

New Point(275, 100), _

New Point(25, 350) _

}

Dim gp As New GraphicsPath

gp.AddPolygon(polypoints)

Dim rgn As New Region(gp)

e.Graphics.ExcludeClip(rgn)

e.Graphics.FillRectangle(Brushes.Red, Me.ClientRectangle)

End Sub

End Class
``````
FillOutsidePolygon.jpg
0

Author Closing Comment

ID: 31565067
Thanks, another perfect solution.
0

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