>I found useful to use transparent controls like:
>
>'----------------------------------------------------------------------------------
>Public Class UserControlTransp
>    Inherits System.Windows.Forms.UserControl
>
>#Region " Windows Form Designer generated code "
>...
>#End Region
>
>    Protected Overrides ReadOnly Property CreateParams() As
>System.Windows.Forms.CreateParams
>        Get
>            Dim MyParams As CreateParams = MyBase.CreateParams()
>            MyParams.ExStyle = MyParams.ExStyle Or &H20
>            Return MyParams
>        End Get
>    End Property
>
>    Protected Overrides Sub OnPaintBackground(ByVal e As
>System.Windows.Forms.PaintEventArgs)
>        ' for transparency
>    End Sub
>
>    Protected Overrides Sub OnPaint(ByVal e As
>System.Windows.Forms.PaintEventArgs)
>        ' Any drawing here ...
>        ControlPaint.DrawBorder3D(e.Graphics, New Rectangle(10, 10,
>200, 100), Border3DStyle.Etched)
>        e.Graphics.FillEllipse(New SolidBrush(Color.FromArgb(100, 120,
>200, 255)), New Rectangle(30, 30, 100, 100))
>    End Sub
>
>End Class
>
>'----------------------------------------------------------------------------------
>
>this allows to draw on a trasparent control surface anything you want.
>
>Does anybody know the corresponding instructions to do the same with a
>Form?
>
>(clearly this is different by setting the form opacity, and allows for
>instance to draw sharp
>pictures on a transparent surface: opacity would instead be inherited
>by images drawn on the form).
>
>-tom

>
> Set Form's Backcolor and TransparencyKey colors to same color.
> Any control with a Backcolor other than the TransparencyKey color, or,
> any drawn graphics using non-key colors will be dispalyed on a
> transparent form background.
>
> With a borderless form, this is one way to create an irregular shaped
> form.
>
> Gene

"tommaso.gasta***@uniroma1.it" wrote:

> Hi Gene, thank you
>
> I am aware of the method you describe. What I was aiming to find is
> something that let me use the form as a purely transparent surface
> where to draw on.
>
> Setting the transparency key is something slightly different. It will
> also affect the drawing.
> And, more importantly, the color removal id done very badly and along
> irregular borders one can often see pixels of the masked color.
>
> I was just hoping there is a simple way to have a clean graphics where
> one can draw and that, at the same time, can be managed as a form...
>
> -tom
>
> gene kelley ha scritto:
>
> >
> > Set Form's Backcolor and TransparencyKey colors to same color.
> > Any control with a Backcolor other than the TransparencyKey color, or,
> > any drawn graphics using non-key colors will be dispalyed on a
> > transparent form background.
> >
> > With a borderless form, this is one way to create an irregular shaped
> > form.
> >
> > Gene
>
>

> Hi,
>
>            Mike Harsh did a msdn tv episode about making non rectangular
> forms using regions.  Maybe that will help you.
>
> http://msdn.microsoft.com/msdntv/episode.aspx?xml=episodes/en/20040401WinFormsMH/manifest.xml
>
> Ken
> ---------------------
>
> "tommaso.gasta***@uniroma1.it" wrote:
>
> > Hi Gene, thank you
> >
> > I am aware of the method you describe. What I was aiming to find is
> > something that let me use the form as a purely transparent surface
> > where to draw on.
> >
> > Setting the transparency key is something slightly different. It will
> > also affect the drawing.
> > And, more importantly, the color removal id done very badly and along
> > irregular borders one can often see pixels of the masked color.
> >
> > I was just hoping there is a simple way to have a clean graphics where
> > one can draw and that, at the same time, can be managed as a form...
> >
> > -tom
> >
> > gene kelley ha scritto:
> >
> > >
> > > Set Form's Backcolor and TransparencyKey colors to same color.
> > > Any control with a Backcolor other than the TransparencyKey color, or,
> > > any drawn graphics using non-key colors will be dispalyed on a
> > > transparent form background.
> > >
> > > With a borderless form, this is one way to create an irregular shaped
> > > form.
> > >
> > > Gene
> >
> >