D2010, TImage. SaveToFile error

[bernhard_LA]

der testcode spielt fehlerfrei; scrollbars sind da und BMP wird korrekt angezeigt.
In der echten Anwendung wird im Hintergrund viel mit atempbmp gemacht,

Delphi-Quellcode:

    processFunctions (  atempbmp )

  
    atempbmp.savetoFile( ......)  //   geht auch noch 
     
    ......

    Image1.Picture.Bitmap.Assign(atempbmp);

      
    Image1.Picture.Bitmap.SaveToFile('c:\temp\out2.bmp');   // geht falsch

Delphi-Quellcode:

unit Unit_savebmp;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    ScrollBox1: TScrollBox;
    Image1: TImage;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormClose(Sender: TObject; var Action: TCloseAction);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }

    atempbmp  : TBitmap;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
       Image1.Picture.LoadFromFile('c:\temp\out.bmp');

       atempbmp.Assign( Image1.Picture.Bitmap);

end;

procedure TForm1.Button2Click(Sender: TObject);
begin
      Image1.Picture.Bitmap.Assign(atempbmp);

      Image1.Picture.Bitmap.SaveToFile('c:\temp\out2.bmp');
end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
     atempbmp.Free;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
    atempbmp :=TBitmap.Create;
end;

end.