再学GDI+[33]: TGPPen

几何变换也就是 Matrix 变换, 画笔的 Matrix 会忽略 dx、dy 平移参数; 选择 LineCapRound 线帽效果比较好.

本例效果图:

代码文件: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.