.NET GDI+: Drawing lines with rounded corners

Question

Given an array of points, it is easy to draw a line based on these, e.g. using the GraphicsPath class.

For instance, the following array of points...

[0]         


        

Answer 1

This is the function I use to draw a rectangle with rounded corners... from this you may calculate the angle of each line.

Public Sub DrawRoundRect(ByVal g As Graphics, ByVal p As Pen, ByVal x As Single, ByVal y As Single, ByVal width As Single, ByVal height As Single, ByVal radius As Single)
    Dim gp As GraphicsPath = New GraphicsPath
    gp.AddLine(x + radius, y, x + width - (radius * 2), y)
    gp.AddArc(x + width - (radius * 2), y, radius * 2, radius * 2, 270, 90)
    gp.AddLine(x + width, y + radius, x + width, y + height - (radius * 2))
    gp.AddArc(x + width - (radius * 2), y + height - (radius * 2), radius * 2, radius * 2, 0, 90)
    gp.AddLine(x + width - (radius * 2), y + height, x + radius, y + height)
    gp.AddArc(x, y + height - (radius * 2), radius * 2, radius * 2, 90, 90)
    gp.AddLine(x, y + height - (radius * 2), x, y + radius)
    gp.AddArc(x, y, radius * 2, radius * 2, 180, 90)
    gp.CloseFigure()
    g.DrawPath(p, gp)
    gp.Dispose()
End Sub

Hope this help you in the harder part of trigonometry ;)

Answer 2

Bezier curves are pretty straightforward to implement:

http://www.codeproject.com/KB/recipes/BezirCurves.aspx

Luckily you also have them as part of the GraphicsPath class if you wanna omit the gory details:

http://msdn.microsoft.com/en-us/library/system.drawing.drawing2d.graphicspath.addbezier.aspx

And you can also look into splines:

http://msdn.microsoft.com/en-us/library/system.drawing.drawing2d.graphicspath.addcurve.aspx

Answer 3

This url has a description of how to draw rounded rectangles that might help you start out.

But I would think that if nothing else you would be able to add more points to your path, to give the illusion of rounded corners. So add in several points between 0,0 and 100,0. An example might be:

(0,0) (90,0) (95,5) (95,10) (0,100)

I have not tested that path in any way, just pulled some numbers that might work out of the air :).