WinAPI: CombineRgn - 区域合成

CombineRgn(

  p1: HRGN;     {合成后的区域}

  p2, p3: HRGN; {两个原始区域}

  p4: Integer   {合并选项; 见下表}

): Integer;     {有四种可能的返回值}



//合并选项:

RGN_AND  = 1;

RGN_OR   = 2;

RGN_XOR  = 3;

RGN_DIFF = 4;

RGN_COPY = 5; {复制第一个区域}



//返回值:

ERROR         = 0; {错误}

NULLREGION    = 1; {空区域}

SIMPLEREGION  = 2; {单矩形区域}

COMPLEXREGION = 3; {多矩形区域}


 
   

本例效果图:

---

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 FormDestroy(Sender: TObject);

    procedure FormActivate(Sender: TObject);

    procedure RadioGroup1Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



var

  Rgn1,Rgn2,Rgn: HRGN;



//初始化

procedure TForm1.FormCreate(Sender: TObject);

begin

  {建立两个原始区域}

  Rgn1 := CreateEllipticRgn(20, 20, 120, 160);

  Rgn2 := CreateEllipticRgn(70, 20, 170, 160);



  {Rgn 是用来接受运算结果的, 但函数 CombineRgn 要求它必须是已存在的区域, 这里虚拟一个}

  Rgn := CreateRectRgnIndirect(BoundsRect);



  RadioGroup1.Items.CommaText := '两个原始区域,RGN_AND,RGN_OR,RGN_XOR,RGN_DIFF,RGN_COPY';

  RadioGroup1.ItemIndex := 0;

end;



//见到窗体时先绘制一次

procedure TForm1.FormActivate(Sender: TObject);

begin

  RadioGroup1Click(nil);

end;



//主要代码

procedure TForm1.RadioGroup1Click(Sender: TObject);

begin

  Repaint;

  if RadioGroup1.ItemIndex = 0 then

  begin

    Canvas.Brush.Color := clSilver;

    Canvas.Brush.Style := bsDiagCross;

    FillRgn(Canvas.Handle, Rgn1, Canvas.Brush.Handle);

    FillRgn(Canvas.Handle, Rgn2, Canvas.Brush.Handle);



    Canvas.Brush.Style := bsSolid;

    Canvas.Brush.Color := clRed;

    FrameRgn(Canvas.Handle, Rgn1, Canvas.Brush.Handle, 2, 2);

    FrameRgn(Canvas.Handle, Rgn2, Canvas.Brush.Handle, 2, 2);

  end else begin

    CombineRgn(Rgn, Rgn1, Rgn2, RadioGroup1.ItemIndex);



    Canvas.Brush.Color := clSilver;

    Canvas.Brush.Style := bsDiagCross;

    FillRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle);



    Canvas.Brush.Style := bsSolid;

    Canvas.Brush.Color := clRed;

    FrameRgn(Canvas.Handle, Rgn, Canvas.Brush.Handle, 2, 2);

  end;

end;



procedure TForm1.FormDestroy(Sender: TObject);

begin

  DeleteObject(Rgn1);

  DeleteObject(Rgn2);

  DeleteObject(Rgn);

end;



end.


 
   

窗体文件:

---

object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 182

  ClientWidth = 300

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  OnActivate = FormActivate

  OnCreate = FormCreate

  OnDestroy = FormDestroy

  PixelsPerInch = 96

  TextHeight = 13

  object RadioGroup1: TRadioGroup

    Left = 189

    Top = 8

    Width = 106

    Height = 166

    Caption = 'RadioGroup1'

    TabOrder = 0

    OnClick = RadioGroup1Click

  end

end