Convert line to polygon

Hi,
Need a help - how to convert a line (polyline) to polygon?

See picture

Well, i find some examples, but nothing to start with
Hope there is visual basic code or algorithm (on c++ etc.)

ps: i've transfer 10k objects map from Visio to Tilemill, and don't find a way to transfer a lines with constant width (KML)

This came from AllAPI:

Code:

---

Private Type COORD
    x As Long
    y As Long
End Type
Private Declare Function CreatePolygonRgn Lib "gdi32" (lpPoint As Any, ByVal nCount As Long, ByVal nPolyFillMode As Long) As Long
Private Declare Function Polygon Lib "gdi32" (ByVal hdc As Long, lpPoint As Any, ByVal nCount As Long) As Long
Private Declare Function FillRgn Lib "gdi32" (ByVal hdc As Long, ByVal hRgn As Long, ByVal hBrush As Long) As Long
Private Declare Function GetStockObject Lib "gdi32" (ByVal nIndex As Long) As Long
Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Const ALTERNATE = 1 ' ALTERNATE and WINDING are
Const WINDING = 2 ' constants for FillMode.
Const BLACKBRUSH = 4 ' Constant for brush type.
Private Sub Form_Paint()
    'KPD-Team 1999
    'URL: http://www.allapi.net/
    'E-Mail: [email protected]
    Dim poly(1 To 3) As COORD, NumCoords As Long, hBrush As Long, hRgn As Long
    Me.Cls
    ' Number of vertices in polygon.
    NumCoords = 3
    ' Set scalemode to pixels to set up points of triangle.
    Me.ScaleMode = vbPixels
    ' Assign values to points.
    poly(1).x = Form1.ScaleWidth / 2
    poly(1).y = Form1.ScaleHeight / 2
    poly(2).x = Form1.ScaleWidth / 4
    poly(2).y = 3 * Form1.ScaleHeight / 4
    poly(3).x = 3 * Form1.ScaleWidth / 4
    poly(3).y = 3 * Form1.ScaleHeight / 4
    ' Polygon function creates unfilled polygon on screen.
    ' Remark FillRgn statement to see results.
    Polygon Me.hdc, poly(1), NumCoords
    ' Gets stock black brush.
    hBrush = GetStockObject(BLACKBRUSH)
    ' Creates region to fill with color.
    hRgn = CreatePolygonRgn(poly(1), NumCoords, ALTERNATE)
    ' If the creation of the region was successful then color.
    If hRgn Then FillRgn Me.hdc, hRgn, hBrush
    DeleteObject hRgn
End Sub
Private Sub Form_Resize()
    Form_Paint
End Sub

---

I tried your code. It's kind different.
Mean that:
http://stackoverflow.com/questions/2...ygon-from-line
http://stackoverflow.com/questions/5...lti-point-line