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type
  TWallpaper = record
    Filename, InfoName: string;
end;

var
  Wallpapers: array of TWallpaper;					

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function GetFileSizeEx(const FileName: String): Int64;
var
  F: TSearchRec;
begin
  Result := - 1;
  if FindFirst(FileName, faAnyFile, F) = 0 then
  begin
    try
      Result := F.FindData.nFileSizeLow or (F.FindData.nFileSizeHigh shl 32);
    finally
      SysUtils.FindClose(F);
    end;
  end;
end;

procedure TMainForm.ShowPreview(Filename: string);
var
  BitmapInfo: TBitmapInfo;
begin
  BitmapInfo := TBitmapInfo.Create;
  try
    BitmapInfo.Filename := Filename;
    BitmapInfo.GetFromFile;
    LB_Info.Clear;
    LB_Info.Items.add('Größe: ' + inttostr(getfilesizeex(Filename) div 1024) + ' Kb');
    LB_Info.Items.add('Breite: ' + inttostr(BitmapInfo.width) + ' Pixel');
    LB_Info.Items.add('Höhe: ' + inttostr(BitmapInfo.height) + ' Pixel');
    LB_Info.Items.add('Farbtiefe: ' + inttostr(BitmapInfo.depth) + ' Bit');
    if (lowercase(extractfileext(Filename)) = '.jpg') or (lowercase(extractfileext(Filename)) = '.jpeg') or (lowercase(extractfileext(Filename)) = '.bmp') then
      IMG_Thumb.Picture.LoadFromFile(Filename);
  finally
    BitmapInfo.Free;
  end;
end;

procedure TMainForm.LB_ListMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
var
  mpos, lbpos: TPoint;
  bsitem: integer;
begin
  if ssright in shift then
  begin
    getcursorpos(mpos);
    PM_Wallpaper.Popup(mpos.x, mpos.y);
  end;
  if ssleft in shift then
  begin
    if LB_List.count < 1 then
      exit;
    lbpos.X := x;
    lbpos.Y := y;
    bsitem := LB_List.ItemAtPos(lbpos, true);
    if bsitem < 0 then
      exit;
    ShowPreview(Wallpapers[bsitem].Filename);
  end;
end;

procedure TMainForm.FormCreate(Sender: TObject);
begin
  SetLength(Wallpapers, 1);
  with IMG_Thumb.Canvas do
  begin
    Brush.Color := clwhite;
    FillRect(IMG_Thumb.ClientRect);
  end;  
end;

procedure TMainForm.Wallpaperhinzufgen1Click(Sender: TObject);
var
  i: integer;
begin
  if openpictureDialog1.Execute then
    for i := 0 to openpicturedialog1.Files.count - 1 do
    begin
      Wallpapers[i].Filename := openpicturedialog1.Files[i];
      Wallpapers[i].InfoName := ExtractFileName(openpicturedialog1.Files[i]);
      LB_List.Items.Add(Wallpapers[i].InfoName);
      SetLength(Wallpapers, length(Wallpapers) + 1);
    end;
end;

procedure TMainForm.LB_ListKeyUp(Sender: TObject; var Key: Word;
  Shift: TShiftState);
var
  bsitem: integer;
  i: integer;
begin
  if (key = vk_left) or (key = vk_right) or (key = vk_up) or (key = vk_down) then
  begin
    if LB_List.count < 1 then
      exit;
    for i := 0 to LB_List.Items.Count - 1 do
      if LB_List.Selected[i] = true then
      begin
        bsitem := i;
        break;
      end;  
    ShowPreview(Wallpapers[bsitem].Filename);
  end;
end;					

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procedure TMainForm.Wallpaperhinzufgen1Click(Sender: TObject);
var
  i: integer;
begin
  if openpictureDialog1.Execute then
    for i := 0 to openpicturedialog1.Files.count - 1 do
    begin
      Wallpapers[length(wallpapers) - 1].Filename := openpicturedialog1.Files[i];
      Wallpapers[length(wallpapers) - 1].InfoName := ExtractFileName(Wallpapers[length(wallpapers) - 1].Filename);
      LB_List.Items.Add(Wallpapers[i].InfoName);
      SetLength(Wallpapers, length(Wallpapers) + 1);
    end;
end;