再学 GDI+[72]: 区域(1) - 建立区域

建立 GDI+ 的区域有五种办法:

1、根据一个矩形建立(矩形区域);
2、根据路径建立;
3、根据 GDI 区域的句柄建立;
4、根据从区域中获取的数据建立;
5、无参数建立.

本例演示了前三种建立方法.

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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, 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 := '矩形通道,椭圆形通道,多边形通道';

  RadioGroup1.ItemIndex := 0;

end;



procedure TForm1.FormPaint(Sender: TObject);

var

  rt: TGPRect;

  pts: array[0..2] of TPoint;

  RgnHandle: HRGN;

  g: TGPGraphics;

  path: TGPGraphicsPath;

  b: TGPBrush;

  rgn: TGPRegion;

begin

  rt := MakeRect(20, 20, 100, ClientHeight-40);

  pts[0] := Point(rt.X + rt.Width div 2, rt.Y);

  pts[1] := Point(rt.X, rt.Y + rt.Height);

  pts[2] := Point(rt.X + rt.Width, rt.Y + rt.Height);



  case RadioGroup1.ItemIndex of

    0: rgn := TGPRegion.Create(rt);       {根据矩形建立(矩形区域)}

    1: begin                              {根据路径建立}

         path := TGPGraphicsPath.Create;

         path.AddEllipse(rt);

         rgn := TGPRegion.Create(path);

         path.Free;

       end;

    2: begin                              {根据 GDI 区域的句柄建立}

         RgnHandle := CreatePolygonRgn(pts, Length(pts), WINDING);

         rgn := TGPRegion.Create(RgnHandle);

         DeleteObject(RgnHandle);

       end;

  end;



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

  b := TGPHatchBrush.Create(HatchStyleDiagonalCross, aclSilver, aclGray);

  g.FillRegion(b, rgn);



  b.Free;

  rgn.Free;

  g.Free;

end;



procedure TForm1.RadioGroup1Click(Sender: TObject);

begin

  Repaint;

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 137

  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 = 121

    Caption = 'RadioGroup1'

    TabOrder = 0

    OnClick = RadioGroup1Click

  end

end