再學 GDI+[33]: TGPPen - 畫筆的幾何變換 - SetTransform

幾何變換也就是 Matrix 變換, 畫筆的 Matrix 會忽略 dx、dy 平移參數; 選擇 LineCapRound 線帽效果比較好.

　　本例效果圖:

　　代碼文件: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;
　　procedure FormCreate(Sender: TObject);
　　procedure FormPaint(Sender: TObject);
　　procedure TrackBar1Change(Sender: TObject);
　　procedure TrackBar2Change(Sender: TObject);
　　procedure TrackBar3Change(Sender: TObject);
　　procedure TrackBar4Change(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;
　TrackBar1.Position := 10;
　TrackBar2.Position := 0;
　TrackBar3.Position := 0;
　TrackBar4.Position := 10;
　Button1.OnClick := FormCreate;
end;
procedure TForm1.FormPaint(Sender: TObject);
var
　g: TGPGraphics;
　b: TGPBrush;
　p: TGPPen;
　matrix: TGPMatrix;
　m11, m12, m21, m22: Single;
begin
　g := TGPGraphics.Create(Canvas.Handle);
　b := TGPHatchBrush.Create(HatchStyleLargeGrid, aclForestGreen);
　p := TGPPen.Create(b, 16);
　m11 := TrackBar1.Position / 10;
　m12 := TrackBar2.Position / 10;
　m21 := TrackBar3.Position / 10;
　m22 := TrackBar4.Position / 10;
　matrix := TGPMatrix.Create(m11, m12, m21, m22, 0, 0);
　p.SetTransform(matrix);
　p.SetStartCap(LineCapRound);
　p.SetEndCap(LineCapRound);
　g.DrawLine(p, 30, 30, ClientWidth - Panel1.Width - 30, ClIEntHeight - 30);
　matrix.Free;
　b.Free;
　p.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;
end.窗體文件:object Form1: TForm1
　Left = 0
　Top = 0
　Caption = 'Form1'
　ClIEntHeight = 184
　ClIEntWidth = 327
　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 = 228
　　Top = 0
　　Width = 99
　　Height = 184
　　Align = alRight
　　TabOrder = 0
　　ExplicitLeft = 225
　　ExplicitHeight = 170
　　object Button1: TButton
　　　Left = 14
　　　Top = 8
　　　Width = 75
　　　Height = 25
　　　Caption = #21021#22987#21270
　　　TabOrder = 0
　　end
　　object TrackBar1: TTrackBar
　　　Left = 0
　　　Top = 39
　　　Width = 100
　　　Height = 20
　　　ShowSelRange = False
　　　TabOrder = 1
　　　OnChange = TrackBar1Change
　　end
　　object TrackBar2: TTrackBar
　　　Left = 0
　　　Top = 72
　　　Width = 100
　　　Height = 20
　　　ShowSelRange = False
　　　TabOrder = 2
　　　OnChange = TrackBar2Change
　　end
　　object TrackBar3: TTrackBar
　　　Left = 0
　　　Top = 106
　　　Width = 100
　　　Height = 20
　　　ShowSelRange = False
　　　TabOrder = 3
　　　OnChange = TrackBar3Change
　　end
　　object TrackBar4: TTrackBar
　　　Left = 0
　　　Top = 140
　　　Width = 100
　　　Height = 20
　　　ShowSelRange = False
　　　TabOrder = 4
　　　OnChange = TrackBar4Change
　　end
　end
end