unit Unit1;interfaceusesWindows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,Dialogs, StdCtrls, CheckLst, ExtCtrls, TeCanvas;typeTForm1 = class(TForm)procedure FormCreate(Sender: TObject);procedure FormDestroy(Sender: TObject);procedure FormPaint(Sender: TObject);procedure FormMouseUp(Sender: TObject; Button: TMouseButton;Shift: TShiftState; X, Y: Integer);procedure FormMouseDown(Sender: TObject; Button: TMouseButton;Shift: TShiftState; X, Y: Integer);end;varForm1: TForm1;implementation{$R *.dfm}uses GDIPOBJ, GDIPAPI;varrect: TGPRect;pt: TGPPoint;pb: TGPPathGradientBrush;procedure TForm1.FormCreate(Sender: TObject);
varpath: TGPGraphicsPath;ColorSurround: TGPColor;  {只用一种包围色, 就别用数组了}num: Integer;
beginrect := MakeRect(10, 10, ClientWidth-20, ClientHeight-20);path := TGPGraphicsPath.Create;path.AddEllipse(rect);pb := TGPPathGradientBrush.Create(path);pb.SetCenterColor(aclLime);pb.GetCenterPoint(pt);ColorSurround := aclBlack;num := 1;pb.SetSurroundColors(@ColorSurround, num);path.Free;DoubleBuffered := True;
end;procedure TForm1.FormDestroy(Sender: TObject);
beginpb.Free;
end;procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;Shift: TShiftState; X, Y: Integer);
beginpt.X := X;pt.Y := Y;Repaint;
end;procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;Shift: TShiftState; X, Y: Integer);
beginRepaint;
end;procedure TForm1.FormPaint(Sender: TObject);
varg: TGPGraphics;p: TGPPen;
beging := TGPGraphics.Create(Canvas.Handle);p := TGPPen.Create(aclRed);g.FillEllipse(pb, rect);pb.SetCenterPoint(pt);g.DrawRectangle(p, pt.X-3, pt.Y-3, 6, 6);p.Free;g.Free;
end;end.

窗体文件:

object Form1: TForm1Left = 0Top = 0Caption = 'Form1'ClientHeight = 164ClientWidth = 208Color = clBtnFaceFont.Charset = DEFAULT_CHARSETFont.Color = clWindowTextFont.Height = -11Font.Name = 'Tahoma'Font.Style = []OldCreateOrder = FalsePosition = poDesktopCenterOnCreate = FormCreateOnDestroy = FormDestroyOnMouseDown = FormMouseDownOnMouseUp = FormMouseUpOnPaint = FormPaintPixelsPerInch = 96TextHeight = 13
end