再学 GDI+[57]: 路径 - Widen

路径的 Widen 方法可以把路径中的线, 根据指定画笔的宽度与样式, 转换为一个范围(有点类似区域); 但转换后再描绘路径就只能使用 FillPath 而不是 DrawPath 了. 本例没有测试它的两个默认参数, 因为前面已多次提到了.

---

本例效果图:

---

代码文件:

---

unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    CheckBox1: TCheckBox;

    CheckBox2: TCheckBox;

    procedure FormCreate(Sender: TObject);

    procedure FormPaint(Sender: TObject);

    procedure CheckBox1Click(Sender: TObject);

    procedure CheckBox2Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



procedure TForm1.FormCreate(Sender: TObject);

begin

  CheckBox1.Caption := '执行 Widen';

  CheckBox2.Caption := '显示路径中所有的点';

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  p: TGPPen;

  b1,b2: TGPBrush;

  path: TGPGraphicsPath;

  pts: array of TGPPoint;

  i: Integer;

begin

  g := TGPGraphics.Create(Canvas.Handle);

  p := TGPPen.Create(aclSlateGray, 20);

  p.SetEndCap(LineCapArrowAnchor);

  b1 := TGPSolidBrush.Create(aclRed);

  b2 := TGPHatchBrush.Create(HatchStyleDiagonalCross, aclSilver, aclSlateGray);



  path := TGPGraphicsPath.Create;

  path.AddLine(40, 50, ClientWidth-40, 50);



  if CheckBox1.Checked then

  begin

    path.Widen(p);

    g.FillPath(b2, path);

  end else g.DrawPath(p, path);



  if CheckBox2.Checked then

  begin

    SetLength(pts, path.GetPointCount);

    path.GetPathPoints(PGPPoint(pts), Length(pts));

    TGPSolidBrush(b1).SetColor(aclRed);

    for i := 0 to Length(pts) - 1 do

      g.FillRectangle(b1, pts[i].X-3, pts[i].Y-3, 6, 6);

  end;



  path.Free;

  b1.Free;

  b2.Free;

  p.Free;

  g.Free;

end;



procedure TForm1.CheckBox1Click(Sender: TObject);

begin

  Repaint;

end;



procedure TForm1.CheckBox2Click(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 136

  ClientWidth = 287

  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 CheckBox1: TCheckBox

    Left = 43

    Top = 104

    Width = 97

    Height = 17

    Caption = 'CheckBox1'

    TabOrder = 0

    OnClick = CheckBox1Click

  end

  object CheckBox2: TCheckBox

    Left = 138

    Top = 104

    Width = 125

    Height = 17

    Caption = 'CheckBox2'

    TabOrder = 1

    OnClick = CheckBox2Click

  end

end