再學 GDI+[62]: 路徑畫刷(2) - SetCenterPoint、GetCenterPoint

本例效果圖:

　　代碼文件:unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls, CheckLst, ExtCtrls, TeCanvas;
type
　TForm1 = 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;
var
　Form1: TForm1;
implementation
{$R *.dfm}
uses GDIPOBJ, GDIPAPI;
var
　rect: TGPRect;
　pt: TGPPoint;
　pb: TGPPathGradIEntBrush;
procedure TForm1.FormCreate(Sender: TObject);
var
　path: TGPGraphicsPath;
　ColorSurround: TGPColor;　{只用一種包圍色, 就別用數組了}
　num: Integer;
begin
　rect := 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);
begin
　pb.Free;
end;
procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
　Shift: TShiftState; X, Y: Integer);
begin
　pt.X := X;
　pt.Y := Y;
　Repaint;
end;
procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
　Shift: TShiftState; X, Y: Integer);
begin
　Repaint;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
　g: TGPGraphics;
　p: TGPPen;
begin
　g := 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.窗體文件:object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClIEntHeight = 164
　ClIEntWidth = 208
　Color = clBtnFace
　Font.Charset = DEFAULT_CHARSET
　Font.Color = clWindowText
　Font.Height = -11
　Font.Name = 'Tahoma'
　Font.Style = []
　OldCreateOrder = False
　Position = poDesktopCenter
　OnCreate = FormCreate
　OnDestroy = FormDestroy
　OnMouseDown = FormMouseDown
　OnMouseUp = FormMouseUp
　OnPaint = FormPaint
　PixelsPerInch = 96
　TextHeight = 13
end