再學 GDI+[14]: DrawBeziers - 繪制一組貝塞爾線

　本例效果圖:

　　代碼文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs;
type
　TForm1 = class(TForm)
　　procedure FormPaint(Sender: TObject);
　　procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
　　　Shift: TShiftState; X, Y: Integer);
　　procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
　　procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
　　　Shift: TShiftState; X, Y: Integer);
　　procedure FormCreate(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ,GDIPAPI;
var
　pts: array of TGPPoint;
　ptn: Integer = -1;
　f: Boolean;
procedure TForm1.FormCreate(Sender: TObject);
begin
　Text := '按住 Ctrl 鍵可添加點';
end;
procedure TForm1.FormPaint(Sender: TObject);
var
　g: TGPGraphics;
　p: TGPPen;
　i: Integer;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　p := TGPPen.Create(aclRed, 1);
　g.Clear(aclWhite);
　g.DrawBezIErs(p, PGPPoint(pts), Length(pts));
　p.SetColor(aclBlue);
　for i := Low(pts) to High(pts) do
　　g.DrawRectangle(p, MakeRect(Rect(pts[i].X-2, pts[i].Y-2, pts[i].X+2, pts[i].Y+2)));
　g.Free;
　p.Free;
end;
procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
　Shift: TShiftState; X, Y: Integer);
begin
　f := True;
end;
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
　Y: Integer);
var
　R: TRect;
　i: Integer;
begin
　if f then
　begin
　　if ptn = -1 then Exit;
　　pts[ptn].X := X;
　　pts[ptn].Y := Y;
　　Repaint;
　end else begin
　　ptn := -1;
　　Cursor := crDefault;
　　for i := Low(pts) to High(pts) do
　　begin
　　　R := Rect(pts[i].X-2, pts[i].Y-2, pts[i].X+2, pts[i].Y+2);
　　　if PtInRect(R, Point(X, Y)) then
　　　begin
　　　　ptn := i;
　　　　Cursor := crHandPoint;
　　　end;
　　end;
　end;
end;
procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
　Shift: TShiftState; X, Y: Integer);
begin
　f := False;
　if ssCtrl in Shift then
　begin
　　SetLength(pts, Length(pts)+1);
　　pts[High(pts)].X := X;
　　pts[High(pts)].Y := Y;
　　Canvas.Pen.Color := clBlue;
　　Canvas.Rectangle(X-2, Y-2, X+2, Y+2);
　　{當點數是 3*n+1 時再繪制}
　　if Length(pts) mod 3 = 1 then Repaint;
　end;
end;
end.窗體文件:object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClIEntHeight = 188
　ClIEntWidth = 254
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　Position = poDesktopCenter
　OnCreate = FormCreate
　OnMouseDown = FormMouseDown
　OnMouseMove = FormMouseMove
　OnMouseUp = FormMouseUp
　OnPaint = FormPaint
　PixelsPerInch = 96
　TextHeight = 13
end