再学GDI+[34]: TGPPen

本例效果图:

代码文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls, ComCtrls;
type
　TForm1 = class(TForm)
　　TrackBar1: TTrackBar;
　　TrackBar2: TTrackBar;
　　procedure FormCreate(Sender: TObject);
　　procedure FormPaint(Sender: TObject);
　　procedure TrackBar1Change(Sender: TObject);
　　procedure TrackBar2Change(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI;
procedure TForm1.FormCreate(Sender: TObject);
begin
　TrackBar1.ShowSelRange := False;
　TrackBar1.Height := 20;
　TrackBar1.Min := 1;
　TrackBar1.Max := 100;
　TrackBar1.Position := 10;
　TrackBar2.ShowSelRange := False;
　TrackBar2.Height := 20;
　TrackBar2.Min := 1;
　TrackBar2.Max := 100;
　TrackBar2.Position := 10;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
　g: TGPGraphics;
　p: TGPPen;
　r: TRect;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　p := TGPPen.Create(aclBrown, 3);
　p.ScaleTransform(TrackBar1.Position / 10, TrackBar2.Position / 10);
　r := ClientRect;
　InflateRect(r, -30, -30);
　OffsetRect(r, 0, -10);
　g.DrawEllipse(p, MakeRect(r));
　p.Free;
　g.Free;
end;
procedure TForm1.TrackBar1Change(Sender: TObject);
begin
　Repaint;
end;
procedure TForm1.TrackBar2Change(Sender: TObject);
begin
　Repaint;
end;
end.