再学 GDI+[34]: TGPPen - 画笔的缩放变换 - ScaleTransform

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, 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.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 196

  ClientWidth = 296

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object TrackBar1: TTrackBar

    Left = 2

    Top = 172

    Width = 143

    Height = 45

    TabOrder = 0

    OnChange = TrackBar1Change

  end

  object TrackBar2: TTrackBar

    Left = 151

    Top = 172

    Width = 143

    Height = 45

    TabOrder = 1

    OnChange = TrackBar2Change

  end

end