procedure IEJoinBitmaps(Dest: TIEBitmap; Src1, Src2: TIEBitmap; Vertical: Boolean; BGColor: TColor = clBlack);
var
  imgLeft, imgTop: Integer;
  totalWidth, totalHeight: Integer;
begin
  if Vertical then
  begin
    totalWidth  := max( Src1.Width, Src2.Width );
    totalHeight := Src1.Height + Src2.Height;
  end
  else
  begin
    totalWidth  := Src1.Width + Src2.Width;
    totalHeight := max( Src1.Height, Src2.Height );
  end;

  Dest.IEInitialize( totalWidth, totalHeight, BGColor );

  if Vertical then
  begin
    imgLeft := ( totalWidth - Src1.Width ) div 2;
    imgTop  := 0;
    Src1.DrawToTIEBitmap( Dest, imgLeft, imgTop );

    imgLeft := ( totalWidth - Src2.Width ) div 2;
    imgTop  := Src1.Height;
    Src2.DrawToTIEBitmap( Dest, imgLeft, imgTop );
  end
  else
  begin
    imgLeft := 0;
    imgTop  := ( totalHeight - Src1.Height ) div 2;
    Src1.DrawToTIEBitmap( Dest, imgLeft, imgTop );

    imgLeft := Src1.Width;
    imgTop  := ( totalHeight - Src2.Height ) div 2;
    Src2.DrawToTIEBitmap( Dest, imgLeft, imgTop );
  end;
end;

procedure IEJoinBitmaps(Dest: TBitmap; Src1, Src2: TBitmap; Vertical: Boolean; BGColor: TColor = clBlack);
var
  imgLeft, imgTop: Integer;
  totalWidth, totalHeight: Integer;
begin
  if Vertical then
  begin
    totalWidth  := max( Src1.Width, Src2.Width );
    totalHeight := Src1.Height + Src2.Height;
  end
  else
  begin
    totalWidth  := Src1.Width + Src2.Width;
    totalHeight := max( Src1.Height, Src2.Height );
  end;

  Dest.IEInitialize( totalWidth, totalHeight, BGColor );

  if Vertical then
  begin
    imgLeft := ( totalWidth - Src1.Width ) div 2;
    imgTop  := 0;
    Dest.Canvas.CopyRect( Rect( imgLeft, imgTop, imgLeft + Src1.Width, imgTop + Src1.Height ),
                          Src1.Canvas,
                          Rect( 0, 0, Src1.Width, Src1.Height ));

    imgLeft := ( totalWidth - Src2.Width ) div 2;
    imgTop  := Src1.Height;
    Dest.Canvas.CopyRect( Rect( imgLeft, imgTop, imgLeft + Src2.Width, imgTop + Src2.Height ),
                          Src2.Canvas,
                          Rect( 0, 0, Src2.Width, Src2.Height ));
  end
  else
  begin
    imgLeft := 0;
    imgTop  := ( totalHeight - Src1.Height ) div 2;
    Dest.Canvas.CopyRect( Rect( imgLeft, imgTop, imgLeft + Src1.Width, imgTop + Src1.Height ),
                          Src1.Canvas,
                          Rect( 0, 0, Src1.Width, Src1.Height ));

    imgLeft := Src1.Width;
    imgTop  := ( totalHeight - Src2.Height ) div 2;
    Dest.Canvas.CopyRect( Rect( imgLeft, imgTop, imgLeft + Src2.Width, imgTop + Src2.Height ),
                          Src2.Canvas,
                          Rect( 0, 0, Src2.Width, Src2.Height ));
  end;
end;

procedure TMain.Button1Click(Sender: TObject);
begin
  ImageEnView1.LegacyBitmap := False;
  ImageEnView2.LegacyBitmap := False;
  ImageEnView3.LegacyBitmap := False;

  ImageEnView1.IO.LoadFromFile( 'D:\_Testfiles\Image1.jpg' );
  ImageEnView2.IO.LoadFromFile( 'D:\_Testfiles\Image2.bmp' );

  IEJoinBitmaps( ImageEnView3.IEBitmap, ImageEnView1.IEBitmap, ImageEnView2.IEBitmap, False );
  ImageEnView3.Update();
end;