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:

---

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