Draw a cardinal spline
#include <GDIPlus.au3>
_GDIPlus_GraphicsDrawCurve ( $hGraphics, $aPoints [, $hPen = 0] )
| $hGraphics | Handle to a Graphics object | 
| $aPoints | Array that specifies the points of the curve: [0][0] - Number of points [1][0] - Point 1 X position [1][1] - Point 1 Y position [2][0] - Point 2 X position [2][1] - Point 2 Y position [n][0] - Point n X position [n][1] - Point n Y position | 
| $hPen | [optional] Handle to a pen object that is used to draw the spline. If 0, a solid black pen with a width of 1 will be used. | 
| Success: | True. | 
| Failure: | False and sets the @error flag to non-zero, @extended may contain GPSTATUS error code ($GDIP_ERR* see GPIPlusConstants.au3). | 
A segment is defined as a curve that connects two consecutive points in the cardinal spline.
The ending point of each segment is the starting point for the next.
Search GdipDrawCurve in MSDN Library.
#include <GDIPlus.au3>
#include <GUIConstantsEx.au3>
Example()
Func Example()
    Local $hGUI, $hGraphic, $aPoints[5][2]
    ; Create GUI
    $hGUI = GUICreate("GDI+", 400, 300)
    GUISetState(@SW_SHOW)
    ; Draw a cardinal spline
    _GDIPlus_Startup()
    $hGraphic = _GDIPlus_GraphicsCreateFromHWND($hGUI)
    $aPoints[0][0] = 4
    $aPoints[1][0] = 0
    $aPoints[1][1] = 100
    $aPoints[2][0] = 50
    $aPoints[2][1] = 50
    $aPoints[3][0] = 100
    $aPoints[3][1] = 100
    $aPoints[4][0] = 150
    $aPoints[4][1] = 50
    _GDIPlus_GraphicsDrawCurve($hGraphic, $aPoints)
    ; Loop until the user exits.
    Do
    Until GUIGetMsg() = $GUI_EVENT_CLOSE
    ; Clean up resources
    _GDIPlus_GraphicsDispose($hGraphic)
    _GDIPlus_Shutdown()
EndFunc   ;==>Example
#include <GDIPlus.au3>
#include <GUIConstantsEx.au3>
Example()
Func Example()
    _GDIPlus_Startup() ;initialize GDI+
    Local Const $iWidth = 600, $iHeight = 600, $iBgColor = 0x303030 ;$iBGColor format RRGGBB
    Local $hGUI = GUICreate("GDI+ Example (" & @ScriptName & ")", $iWidth, $iHeight) ;create a test GUI
    GUISetBkColor($iBgColor, $hGUI) ;set GUI background color
    GUISetState(@SW_SHOW)
    Local $hGraphics = _GDIPlus_GraphicsCreateFromHWND($hGUI) ;create a graphics object from a window handle
    _GDIPlus_GraphicsSetSmoothingMode($hGraphics, $GDIP_SMOOTHINGMODE_HIGHQUALITY) ;sets the graphics object rendering quality (antialiasing)
    Local $hPen = _GDIPlus_PenCreate(0xFFFFFFFF, 4) ;color format AARRGGBB (hex)
    Local $aPoints[8][2]
    $aPoints[0][0] = 7
    $aPoints[1][0] = 50.5
    $aPoints[1][1] = 50.5
    $aPoints[2][0] = 100.75
    $aPoints[2][1] = 25.33
    $aPoints[3][0] = 200.66
    $aPoints[3][1] = 5.5
    $aPoints[4][0] = 250.25
    $aPoints[4][1] = 50.75
    $aPoints[5][0] = 300.125
    $aPoints[5][1] = 100.375
    $aPoints[6][0] = 590.8
    $aPoints[6][1] = 200.222
    $aPoints[7][0] = 250.55
    $aPoints[7][1] = 590.45
    _GDIPlus_GraphicsDrawCurve($hGraphics, $aPoints, $hPen)
    Do
    Until GUIGetMsg() = $GUI_EVENT_CLOSE
    ;cleanup GDI+ resources
    _GDIPlus_PenDispose($hPen)
    _GDIPlus_GraphicsDispose($hGraphics)
    _GDIPlus_Shutdown()
    GUIDelete($hGUI)
EndFunc   ;==>Example