再学 GDI+[73]: 区域(2) - 区域运算

Intersect  {交集}

Union      {联合}

Xor_       {减去交集}

Exclude    {减去}

Complement {不相交}



//GDI+ 的区域能和矩形、路径、另一个区域三种对象进行运算.


 
   

本例效果图:

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代码文件:

---

unit Unit1;



interface



uses

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

  Dialogs, StdCtrls, ExtCtrls;



type

  TForm1 = class(TForm)

    RadioGroup1: TRadioGroup;

    procedure FormCreate(Sender: TObject);

    procedure FormPaint(Sender: TObject);

    procedure RadioGroup1Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses GDIPOBJ, GDIPAPI;



procedure TForm1.FormCreate(Sender: TObject);

begin

  RadioGroup1.Items.CommaText := '通道,矩形,Intersect,Union,Xor_,Exclude,Complement';

  RadioGroup1.ItemIndex := 0;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  g: TGPGraphics;

  p: TGPPen;

  path: TGPGraphicsPath;

  b: TGPBrush;

  rgn: TGPRegion;

  rt: TGPRect;

begin

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

  p := TGPPen.Create(MakeColor(100, 255, 0, 0));

  b := TGPHatchBrush.Create(HatchStyleSmallGrid, aclSilver, aclCornflowerBlue);



  {准备个路径}

  path := TGPGraphicsPath.Create;

  path.AddEllipse(20, 20, 100, 80);



  {根据路径建立区域}

  rgn := TGPRegion.Create(path);



  {获取距形}

//  rgn.GetBounds(rt, g);

  path.GetBounds(rt);



  {下移矩形, 将用此矩形与上面的区域进行运算}

  rt.Y := rt.Y + rt.Height div 2;



  case RadioGroup1.ItemIndex of

    1: rgn := TGPRegion.Create(rt);

    2: rgn.Intersect(rt);

    3: rgn.Union(rt);

    4: rgn.Xor_(rt);

    5: rgn.Exclude(rt);

    6: rgn.Complement(rt);

  end;



  g.FillRegion(b, rgn);

  g.DrawPath(p, path);

  g.DrawRectangle(p, rt);



  b.Free;

  rgn.Free;

  p.Free;

  g.Free;

end;



procedure TForm1.RadioGroup1Click(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 167

  ClientWidth = 238

  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 RadioGroup1: TRadioGroup

    Left = 137

    Top = 8

    Width = 91

    Height = 151

    Caption = 'RadioGroup1'

    TabOrder = 0

    OnClick = RadioGroup1Click

  end

end