再学 GDI+[62]: 路径画刷(2) - SetCenterPoint、GetCenterPoint

本例效果图:

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代码文件:

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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;  {只用一种包围色, 就别用数组了}

  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.


 
   

窗体文件:

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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