How to screenshot only the area inside an Ellipse? - vb.net

Question

I'm creating a little snipping tool-like program in VB.NET and I can screenshot any area I want provided it is a rectangle area. I select the area in the screen and save it as an image. That's easy.
My problem is that I want to be able to screenshot not only a rectangular (standard rectangle shape area), but selecting/drawing an ellipse and screenshot the inside part of it. See the image below:
is there any way to achieve this or any library I can use for that?
Here's my current code:
Public Class Form3
Private _bRubberBandingOn As Boolean = False
Private _pClickStart As New Point
Private _pClickStop As New Point
Private _pNow As New Point
Private Sub Form3_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
Me._bRubberBandingOn = Not _bRubberBandingOn
If Me._bRubberBandingOn Then
If _pClickStart = Nothing Then _pClickStart = New Point
_pClickStart.X = e.X
_pClickStart.Y = e.Y
_pNow.X = e.X
_pNow.Y = e.Y
End If
Me.Invalidate()
End Sub
Private Sub Form3_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
If Me._bRubberBandingOn Then
If _pNow = Nothing Then _pNow = New Point
Me._pNow.X = e.X
Me._pNow.Y = e.Y
Me.Invalidate()
End If
End Sub
Private Sub Form3_MouseUp(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp
Me._bRubberBandingOn = Not Me._bRubberBandingOn
If Not Me._bRubberBandingOn Then
If _pClickStop = Nothing Then _pClickStop = New Point
_pClickStop.X = e.X
_pClickStop.Y = e.Y
Me.Invalidate()
End If
End Sub
Private Sub Form3_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
Dim _rRectangle As New Rectangle
Dim _penNew As New Pen(Color.Black, 2)
_rRectangle.X = _pClickStart.X
_rRectangle.Y = _pClickStart.Y
If Me._bRubberBandingOn Then
_rRectangle.Width = Me._pNow.X - _pClickStart.X
_rRectangle.Height = Me._pNow.Y - _pClickStart.Y
Else
_rRectangle.Width = Me._pClickStop.X - _pClickStart.X
_rRectangle.Height = Me._pClickStop.Y - _pClickStart.Y
End If
_penNew.DashStyle = Drawing2D.DashStyle.Solid
e.Graphics.DrawEllipse(_penNew, _rRectangle)
End Sub
End Class
Is there any way to achieve this or any library I can use for that?
Is it any way to get a handle of that painted line/shape and then use it to create a screenshot? I actually searched about this but didn't found anything meaningful yet.
thanks in advance for your time.

Answer 1

Take the image that you are drawing the ellipse on top of and do the following:
Dim theBitmap As Bitmap = DirectCast(Image.FromFile("PathToFileYouAreDrawingEllipseOn.bmp"), Bitmap)
Dim theEllipseBitmap As New Bitmap(theBitmap.Width, theBitmap.Height)
Dim theGraphics As Graphics = Graphics.FromImage(theEllipseBitmap)
Dim theGraphicsPath As New GraphicsPath()
' The (10,10) coordinates here are made up, you will need to take what is drawn by the user (starting x,y; ending x,y, etc.)
theGraphicsPath.AddEllipse(10, 10, theBitmap.Width - 20, theBitmap.Height - 20)
theGraphics.Clear(Color.Magenta)
theGraphics.SetClip(theGraphicsPath)
theGraphics.DrawImage(theBitmap, New Rectangle(0, 0, theBitmap.Width, theBitmap.Height), 0, 0, theBitmap.Width, theBitmap.Height, _
GraphicsUnit.Pixel)
theGraphics.Dispose()
theEllipseBitmap.MakeTransparent(Color.Magenta)
' Save the ellipse bitmap to a PNG file format
string fileName = "PathToYourDesiredOutput.png"
theEllipseBitmap.Save(fileName, System.Drawing.Imaging.ImageFormat.Png)