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.

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.

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