剪切區域也是區域的一種, 窗口在重繪時只會重繪剪切區域中的內容.
SelectClipRgn 和 ExtSelectClipRgn 是通過指定區域來定義剪切區域;
SelectClipPath 是通過指定路徑來定義剪切區域;
ExtSelectClipRgn 和 SelectClipPath 比 SelectClipRgn 多出一個與原剪切區域混合方式的參數:
RGN_AND = 1;
RGN_OR = 2;
RGN_XOR = 3;
RGN_DIFF = 4;
RGN_COPY = 5;
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 FormDestroy(Sender: TObject);
procedure FormPaint(Sender: TObject);
procedure RadioGroup1Click(Sender: TObject);
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
var
bit: TBITMAP;
procedure TForm1.FormCreate(Sender: TObject);
begin
RadioGroup1.Caption := '定義剪切區域';
RadioGroup1.Items.CommaText := '無剪切區域,根據區域,根據路徑';
RadioGroup1.ItemIndex := 0;
bit := TBitmap.Create;
bit.LoadFromFile('c:\temp\Test.bmp');
end;
procedure TForm1.FormPaint(Sender: TObject);
var
Rgn: HRGN;
begin
case RadioGroup1.ItemIndex of
1: begin
Rgn := CreateEllipticRgn(30,30,140,140);
SelectClipRgn(Canvas.Handle, Rgn);
DeleteObject(Rgn);
end;
2: begin
Canvas.Font.Size := 160;
Canvas.Font.Style := [fsBold];
SetBkMode(Canvas.Handle, TRANSPARENT);
BeginPath(Canvas.Handle);
Canvas.TextOut(-15,-30,'A');
EndPath(Canvas.Handle);
SelectClipPath(Canvas.Handle, RGN_COPY);
end;
end;
Canvas.Draw(0,0,bit);
end;
procedure TForm1.RadioGroup1Click(Sender: TObject);
begin
Repaint;
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
bit.Free;
end;
end.
窗體文件:
object Form1: TForm1
Left = 366
Top = 307
Caption = 'Form1'
ClIEntHeight = 206
ClIEntWidth = 309
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
Position = poDesigned
OnCreate = FormCreate
OnDestroy = FormDestroy
OnPaint = FormPaint
PixelsPerInch = 96
TextHeight = 13
object RadioGroup1: TRadioGroup
Left = 209
Top = 93
Width = 95
Height = 105
Caption = 'RadioGroup1'
TabOrder = 0
OnClick = RadioGroup1Click
end
end
