Re-learning gdi+[73]: Area (2)

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.

This example effect chart:

Code files: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: = ' channel, rectangle, 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);
{Prepare a path}
Path: = Tgpgraphicspath.create;
Path. AddEllipse (20, 20, 100, 80);
{Create zone based on path}
Rgn: = tgpregion.create (path);
{Get spacing}
Rgn. GetBounds (RT, G);
Path. GetBounds (RT);
{Move the rectangle down, and use this rectangle to perform the operation on the above area}
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.

Form file: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