再学 GDI+[59]: 路径 - TGPGraphicsPathIterator

通过路径的辅助类 TGPGraphicsPathIterator , 可以获得更多路径数据和控制能力.

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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;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    procedure FormCreate(Sender: TObject);

    procedure FormDestroy(Sender: TObject);

    procedure FormPaint(Sender: TObject);

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



var

  path: TGPGraphicsPath;



procedure TForm1.FormCreate(Sender: TObject);

var

  pt1, pt2: TPoint;

begin

  Button1.Caption := '查看路径基本数据';

  Button2.Caption := '重绘路径中的子路径';



  pt1 := Point(30, 20);

  pt2 := Point(150, 120);



  {建立路径, 并添加四个子图形}

  path := TGPGraphicsPath.Create;

  path.StartFigure;

  path.AddRectangle(MakeRect(Rect(pt1, pt2)));

  path.CloseFigure;



  path.StartFigure;

  path.AddEllipse(MakeRect(Rect(pt1, pt2)));

  path.CloseFigure;



  path.StartFigure;

  path.AddLine(pt1.X, pt1.Y, pt2.X, pt2.Y);

  path.CloseFigure;



  path.StartFigure;

  path.AddLine(pt1.X, pt2.Y, pt2.X, pt1.Y);

  path.CloseFigure;

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  path.Free;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  p: TGPPen;

begin

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

  p := TGPPen.Create(aclSilver, 2);

  g.DrawPath(p, path);

  p.Free;

  g.Free;

end;



procedure TForm1.Button1Click(Sender: TObject);

var

  PathIterator: TGPGraphicsPathIterator;

  str: string;

begin

  PathIterator := TGPGraphicsPathIterator.Create(path);

  str := str + Format('路径中的总点数: %d', [PathIterator.GetCount]);

  str := str + Format(sLineBreak + '路径中的子路径数: %d', [PathIterator.GetSubpathCount]);

  str := str + Format(sLineBreak + '路径中是否包含曲线: %s', [BoolToStr(PathIterator.HasCurve, True)]);

  ShowMessage(str);

  PathIterator.Free;

end;



procedure TForm1.Button2Click(Sender: TObject);

const

  ColorArr: array[0..3] of TGPColor = (aclRed, aclGreen, aclBlue, aclYellow);

var

  PathIterator: TGPGraphicsPathIterator;

  PathSection: TGPGraphicsPath;

  bool: LongBool;

  g: TGPGraphics;

  p: TGPPen;

  i: Integer;

begin

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

  p := TGPPen.Create(aclRed, 2);

  PathIterator := TGPGraphicsPathIterator.Create(path);



  PathIterator.Rewind; {到路径起始点}

  for i := 0 to PathIterator.GetSubpathCount - 1 do

  begin

    PathSection := TGPGraphicsPath.Create;

    PathIterator.NextSubpath(PathSection, bool);

    p.SetColor(ColorArr[i]);

    g.DrawPath(p, PathSection);

    PathSection.Free;

  end;



  PathIterator.Free;

  p.Free;

  g.Free;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 198

  ClientWidth = 181

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnDestroy = FormDestroy

  OnPaint = FormPaint

  PixelsPerInch = 96

  TextHeight = 13

  object Button1: TButton

    Left = 24

    Top = 134

    Width = 137

    Height = 25

    Caption = 'Button1'

    TabOrder = 0

    OnClick = Button1Click

  end

  object Button2: TButton

    Left = 24

    Top = 165

    Width = 137

    Height = 25

    Caption = 'Button2'

    TabOrder = 1

    OnClick = Button2Click

  end

end