copyrect用法

unit Unit1;
interface
uses
 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
 PicShow, StdCtrls, ExtCtrls;
type
 TForm1 = class(TForm)
   Image1: TImage;
   Image2: TImage;
   Button1: TButton;
   procedure Button1Click(Sender: TObject);
 private
   { Private declarations }
 public
   { Public declarations }
//    th:tthreat;
 end;
var
 Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.Button1Click(Sender: TObject);
const
step=4;
var
r:trect;
i:integer;
begin
image2.Canvas.FillRect(rect(0,0,image2.Width,image2.Height));
image2.Canvas.CopyMode:=cmsrccopy;
i:=0;
repeat
r:=rect(i,0,i+step,image1.Height);
sleep(10);
image2.Canvas.CopyRect(r,image1.Canvas,r);
application.ProcessMessages;
inc(i,step);
until i>image1.Width;
image2.Picture.Bitmap.SaveToFile('c:\windows\desktop\temp.bmp');
end;
end.

object Form1: TForm1
 Left = 63
 Top = 57
 Width = 712
 Height = 453
 Caption = 'Form1'
 Color = clBtnFace
 Font.Charset = DEFAULT_CHARSET
 Font.Color = clWindowText
 Font.Height = -11
 Font.Name = 'MS Sans Serif'
 Font.Style = []
 OldCreateOrder = False
 PixelsPerInch = 96
 TextHeight = 13
 object Image1: TImage
   Left = 0
   Top = 0
   Width = 355
   Height = 426
   Align = alLeft
   Stretch = True
 end
 object Image2: TImage
   Left = 355
   Top = 0
   Width = 349
   Height = 426
   Align = alClient
 end
 object Button1: TButton
   Left = 328
   Top = 192
   Width = 75
   Height = 25
   Caption = 'Button1'
   TabOrder = 0
   OnClick = Button1Click
 end
end