GDI+ 紋理筆刷與矩陣變換：TGPTextureBrush 搭配 TGPMatrix

TGPTextureBrush 使用圖像作為填充紋理，配合 TGPMatrix 仿射變換矩陣，可實現紋理的縮放、旋轉、傾斜、平移等幾何變換，極大擴展紋理填充的表現力。

核心概念

• TGPTextureBrush：以 TGPImage 為紋理來源的筆刷
• TGPMatrix：3×3 仿射變換矩陣，包含 6 個參數 (m11, m12, m21, m22, dx, dy)
• SetTransform：將矩陣套用至筆刷，影響後續填充操作

矩陣參數對應關係：

• m11, m22：X、Y 方向縮放
• m12, m21：X、Y 方向傾斜
• dx, dy：X、Y 方向平移

程式碼實作

六個軌跡條分別控制矩陣六個參數，即時觀察紋理變換效果：

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ComCtrls, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Panel1: TPanel;
    Button1: TButton;
    TrackBar1: TTrackBar;
    TrackBar2: TTrackBar;
    TrackBar3: TTrackBar;
    TrackBar4: TTrackBar;
    TrackBar5: TTrackBar;
    TrackBar6: TTrackBar;
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure TrackBar1Change(Sender: TObject);
    procedure TrackBar2Change(Sender: TObject);
    procedure TrackBar3Change(Sender: TObject);
    procedure TrackBar4Change(Sender: TObject);
    procedure TrackBar5Change(Sender: TObject);
    procedure TrackBar6Change(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}
uses GDIPOBJ, GDIPAPI;

procedure TForm1.FormCreate(Sender: TObject);
const
  n = 40;
begin
  TrackBar1.Min := -n; TrackBar1.Max := n;
  TrackBar2.Min := -n; TrackBar2.Max := n;
  TrackBar3.Min := -n; TrackBar3.Max := n;
  TrackBar4.Min := -n; TrackBar4.Max := n;
  TrackBar5.Min := -n; TrackBar5.Max := n;
  TrackBar6.Min := -n; TrackBar6.Max := n;
  TrackBar1.Position := 10;
  TrackBar2.Position := 0;
  TrackBar3.Position := 0;
  TrackBar4.Position := 10;
  TrackBar5.Position := 0;
  TrackBar6.Position := 0;
  Button1.OnClick := FormCreate;
end;

procedure TForm1.FormPaint(Sender: TObject);
var
  g: TGPGraphics;
  img: TGPImage;
  tb: TGPTextureBrush;
  matrix: TGPMatrix;
  m11, m12, m21, m22, dx, dy: Single;
begin
  g := TGPGraphics.Create(Canvas.Handle);
  img := TGPImage.Create('c:\temp\small.png');
  tb := TGPTextureBrush.Create(img);
  m11 := TrackBar1.Position / 10;
  m12 := TrackBar2.Position / 10;
  m21 := TrackBar3.Position / 10;
  m22 := TrackBar4.Position / 10;
  dx := TrackBar5.Position * 10;
  dy := TrackBar6.Position * 10;
  matrix := TGPMatrix.Create(m11, m12, m21, m22, dx, dy);
  tb.SetTransform(matrix);
  g.FillRectangle(tb, 0, 0, ClientWidth - Panel1.Width, ClientHeight);
  matrix.Free;
  img.Free;
  tb.Free;
  g.Free;
end;

procedure TForm1.TrackBar1Change(Sender: TObject); begin Repaint; end;
procedure TForm1.TrackBar2Change(Sender: TObject); begin Repaint; end;
procedure TForm1.TrackBar3Change(Sender: TObject); begin Repaint; end;
procedure TForm1.TrackBar4Change(Sender: TObject); begin Repaint; end;
procedure TForm1.TrackBar5Change(Sender: TObject); begin Repaint; end;
procedure TForm1.TrackBar6Change(Sender: TObject); begin Repaint; end;

end.

表單設計 (DFM)

object Form1: TForm1
  Left = 0
  Top = 0
  Caption = 'Form1'
  ClientHeight = 170
  ClientWidth = 324
  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 Panel1: TPanel
    Left = 225
    Top = 0
    Width = 99
    Height = 170
    Align = alRight
    TabOrder = 0
    ExplicitLeft = 288
    ExplicitHeight = 213
    object Button1: TButton
      Left = 14
      Top = 8
      Width = 75
      Height = 25
      Caption = #21021#22987#21270
      TabOrder = 0
    end
    object TrackBar1: TTrackBar
      Left = 0
      Top = 34
      Width = 100
      Height = 20
      ShowSelRange = False
      TabOrder = 1
      OnChange = TrackBar1Change
    end
    object TrackBar2: TTrackBar
      Left = 0
      Top = 56
      Width = 100
      Height = 20
      ShowSelRange = False
      TabOrder = 2
      OnChange = TrackBar2Change
    end
    object TrackBar3: TTrackBar
      Left = 0
      Top = 78
      Width = 100
      Height = 20
      ShowSelRange = False
      TabOrder = 3
      OnChange = TrackBar3Change
    end
    object TrackBar4: TTrackBar
      Left = 0
      Top = 100
      Width = 100
      Height = 20
      ShowSelRange = False
      TabOrder = 4
      OnChange = TrackBar4Change
    end
    object TrackBar5: TTrackBar
      Left = 0
      Top = 122
      Width = 100
      Height = 20
      ShowSelRange = False
      TabOrder = 5
      OnChange = TrackBar5Change
    end
    object TrackBar6: TTrackBar
      Left = 0
      Top = 144
      Width = 100
      Height = 20
      ShowSelRange = False
      TabOrder = 6
      OnChange = TrackBar6Change
    end
  end
end

執行效果

調整軌跡條可即時看到紋理的縮放、傾斜、平移效果。按下「重置」按鈕恢復預設矩陣 (單位矩陣)。掌握矩陣變換是進階 2D 圖形程式設計的核心技能。