[RESOLVED] Flip a GraphicsPath onto itself

[i00]

Ok... I have a graphics path ... and I want it to be symmetrical ... so I thought I would just draw the right 1/2 with positive X values... then use 0-x on the points x values to flip it by cloning and reversing the PathData ...

but I can't seem to be able to append to point data??

I was doing it like this:

gpPerson.PathData.Points = gpPerson.PathData.Points.ToArray.Concat(gpPerson.PathData.Points.ToArray.Select(Function(x) New PointF(-x.X, x.Y)).Reverse).ToArray
            gpPerson.PathData.Types = gpPerson.PathData.Types.ToArray.Concat(gpPerson.PathData.Types.ToArray.Reverse).ToArray

'I went abit overboard with the .ToArray's above while I was testing

Any ideas how I could do this?

Also I don't want to just flip it with a transformation and redraw the 2nd 1/2 separately... I want it to be the one graphics path.

Thanks,
Kris

[boops boops]

Flip and translate the path by whatever means you see fit. Then add it back to the original path with AddPath. Here's an example that does use a matrix for flip and translate:

	Private Function ReflectPath(gp As Drawing2D.GraphicsPath) As Drawing2D.GraphicsPath
		Using mirror As New Drawing2D.GraphicsPath(gp.PathPoints, gp.PathTypes)
			Dim mtx As New Drawing2D.Matrix(-1, 0, 0, 1, gp.GetBounds.Width * 2.1F, 0) 'flip and translate X
			mirror.Transform(mtx)
			gp.AddPath(mirror, False)
		End Using
		Return gp
	End Function

BB

[i00]

Thanks... Almost there, but... I need the paths to be connected ... and the problem with this is shown below (I expanded the gap in between the mirror a little so that you can see what is going on)... this is why I reversed it in my example ...



Thanks again,
Kris

[boops boops]

To prevent the cross-line, reverse the direction of the reflected part with GraphicsPath.Reverse. Add CloseFigure to complete the joins. See the improved version of the ReflectPath function in this little ready-to-run example. Scribble with the left mouse button to see the effect.

Public Class Form1

	Private startDraw As Point
	Private pth, dblPath As Drawing2D.GraphicsPath

	Private Sub Form1_MouseDown(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseDown
		If e.Button = Windows.Forms.MouseButtons.Left Then
			pth = New Drawing2D.GraphicsPath
			dblPath = New Drawing2D.GraphicsPath
			startDraw = e.Location
		End If
	End Sub

	Private Sub Form1_MouseMove(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
		If e.Button = Windows.Forms.MouseButtons.Left Then
			pth.AddLine(startDraw, e.Location)
			startDraw = e.Location
			Me.Invalidate()
		End If
	End Sub

	Private Sub Form1_MouseUp(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseUp
		dblPath = ReflectPath(pth)
		Me.Invalidate()
	End Sub

	Private Sub Form1_Paint(sender As Object, e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
		If dblPath IsNot Nothing Then
			Using pn As New Pen(Color.Red, 2)
				e.Graphics.DrawPath(pn, dblPath)
			End Using
		End If
		If pth IsNot Nothing Then
			Using pn As New Pen(Color.Gray, 2)
				e.Graphics.DrawPath(pn, pth)
			End Using
		End If
	End Sub

	Private Function ReflectPath(gp As Drawing2D.GraphicsPath) As Drawing2D.GraphicsPath		
		Dim Xtranslation As Single = 2 * gp.GetBounds.Right
		Dim mtx As New Drawing2D.Matrix(-1, 0, 0, 1, Xtranslation, 0)
		Dim pth As New Drawing2D.GraphicsPath(gp.PathPoints, gp.PathTypes)
		Using mirror As New Drawing2D.GraphicsPath(gp.PathPoints, gp.PathTypes)
			mirror.Transform(mtx)
			mirror.Reverse()
			pth.AddPath(mirror, True)
			pth.CloseFigure()
		End Using
		Return pth
	End Function

End Class

You may need to play around with the XTranslation value to get the two halves to line up nicely. 2*GetBounds.Right worked out in the above example but I am not sure if it will apply in your code.

BB

[passel]

Isn't checking for left mouse in the Mouse Up event so, ......
drag with the left mouse, and tap the right mouse periodically while continuing to drag with the left, for interesting side effect.
Wasn't trying to draw anything, just a few back and forth up the form with periodic right clicks, and release, and it looks rather bunny like to me.

[i00]

Thanks... didn't know about the GraphicsPath.Reverse

I did it mirroring from x=0 so made it:

Private Shared Function ReflectPath(gp As Drawing2D.GraphicsPath) As Drawing2D.GraphicsPath
        Dim Xtranslation As Single = 2 * gp.GetBounds.Right
        Dim pth As New Drawing2D.GraphicsPath(gp.PathPoints, gp.PathTypes)
        Using mirror As New Drawing2D.GraphicsPath(gp.PathPoints, gp.PathTypes)
            Using mtx As New Drawing2D.Matrix
                mtx.Scale(-1, 1)
                mirror.Transform(mtx)
            End Using
            mirror.Reverse()
            pth.AddPath(mirror, True)
            pth.CloseFigure()
        End Using
        Return pth
    End Function

Works like a treat now ... thanks for all of your help ... karma given!
Kris