再学GDI+[5]: DrawArc

本例效果图:

代码文件: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.