再学 GDI+[79]: 区域(8) - Transform - 区域的 Matrix 变换

矩阵变换(Matrix)功能很强大, 这里只是旋转了一下.

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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;
    procedure FormPaint(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure TrackBar1Change(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormCreate(Sender: TObject);
begin
  TrackBar1.Min := -45;
  TrackBar1.Max := 45;

  DoubleBuffered := True;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  b: TGPBrush;
  rgn: TGPRegion;
  Matrix: TGPMatrix;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  b := TGPHatchBrush.Create(HatchStyleMin, aclSilver, aclChocolate);
  rgn := TGPRegion.Create(MakeRect(40, 40, ClientWidth-80, ClientHeight-100));

  Matrix := TGPMatrix.Create;
  Matrix.Rotate(TrackBar1.Position);
  rgn.Transform(Matrix);

  g.FillRegion(b, rgn);

  Matrix.Free;
  rgn.Free;
  b.Free;
  g.Free;
end;

procedure TForm1.TrackBar1Change(Sender: TObject);
begin
  Repaint;
end;

end.

窗体文件:

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object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 174
  ClientWidth = 197
  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 = 0
    Top = 151
    Width = 193
    Height = 23
    ShowSelRange = False
    TabOrder = 0
    OnChange = TrackBar1Change
  end
end