再學 GDI+[5]: DrawArc - 繪制弧線

　本例效果圖:

　　代碼文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls, Spin, ExtCtrls;
type
　TForm1 = class(TForm)
　　Panel1: TPanel;
　　Label1: TLabel;
　　Label2: TLabel;
　　SpinEdit1: TSpinEdit;
　　SpinEdit2: TSpinEdit;
　　procedure FormCreate(Sender: TObject);
　　procedure FormPaint(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI;
var
　a1,a2: Integer;
procedure TForm1.FormCreate(Sender: TObject);
begin
　a1 := 0;
　a2 := 360;
　SpinEdit1.Text := IntToStr(a1);
　SpinEdit2.Text := IntToStr(a2);
　SpinEdit1.Increment := 10;
　SpinEdit2.Increment := 10;
　SpinEdit1.OnChange := FormPaint;
　SpinEdit2.OnChange := FormPaint;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
　g: TGPGraphics;
　p: TGPPen;
　x,y,w,h: Integer;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　p := TGPPen.Create(aclRed, 2);
　g.Clear(aclWhite);
　x := ClIEntWidth div 6;
　y := ClIEntHeight div 6;
　w := x * 4;
　h := y * 3;
　a1 := StrToIntDef(SpinEdit1.Text, 0);
　a2 := StrToIntDef(SpinEdit2.Text, 360);
　g.DrawArc(p, x, y, w, h, a1, a2);
　g.Free;
　p.Free;
end;
end.窗體文件:object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClIEntHeight = 184
　ClIEntWidth = 258
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　Position = poDesktopCenter
　OnCreate = FormCreate
　OnPaint = FormPaint
　PixelsPerInch = 96
　TextHeight = 13
　object Panel1: TPanel
　　Left = 0
　　Top = 151
　　Width = 258
　　Height = 33
　　Align = alBottom
　　BevelOuter = bvNone
　　TabOrder = 0
　　ExplicitLeft = 8
　　ExplicitTop = 96
　　ExplicitWidth = 257
　　object Label2: TLabel
　　　Left = 136
　　　Top = 8
　　　Width = 52
　　　Height = 13
　　　Caption = #26059#36716#35282#24230':'
　　end
　　object Label1: TLabel
　　　Left = 8
　　　Top = 8
　　　Width = 52
　　　Height = 13
　　　Caption = #36215#22987#35282#24230':'
　　end
　　object SpinEdit2: TSpinEdit
　　　Left = 194
　　　Top = 3
　　　Width = 55
　　　Height = 22
　　　MaxValue = 0
　　　MinValue = 0
　　　TabOrder = 0
　　　Value = 0
　　end
　　object SpinEdit1: TSpinEdit
　　　Left = 66
　　　Top = 3
　　　Width = 55
　　　Height = 22
　　　MaxValue = 0
　　　MinValue = 0
　　　TabOrder = 1
　　　Value = 0
　　end
　end
end