再學 GDI+[73]: 區域(2) - 區域運算

Intersect　{交集}
Union　　　{聯合}
Xor_　　　 {減去交集}
Exclude　　{減去}
Complement {不相交}
//GDI+ 的區域能和矩形、路徑、另一個區域三種對象進行運算.本例效果圖:

　　代碼文件: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);
　{准備個路徑}
　path := TGPGraphicsPath.Create;
　path.AddEllipse(20, 20, 100, 80);
　{根據路徑建立區域}
　rgn := TGPRegion.Create(path);
　{獲取距形}
//　rgn.GetBounds(rt, g);
　path.GetBounds(rt);
　{下移矩形, 將用此矩形與上面的區域進行運算}
　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.窗體文件: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