procedure TForm1.DrawHorzontally1Click(Sender: TObject);
var
  i: Integer;
  iIndex: Integer;
  iIEBitmapSource: TIEBitmap;
  iCheckedCounter: Integer;
  iBitmapSourceWidth: Integer;
  iBitmapSourceHeight: Integer;
begin
  Screen.Cursor := crHourGlass;
  try
    ImageEnView1.Clear;
    // Create a TIEbitmap to hold the source image
    iIEBitmapSource := TIEBitmap.Create;
    try
      iBitmapSourceWidth := ImageEnView1.ClientWidth - 350;//1024;
      iBitmapSourceHeight := ImageEnView1.ClientHeight; //768;
      // Set the ImageEnView IEBitmap width to iBitmapSourceWidth * the number of checked images
      ImageEnView1.IEBitmap.Width := iBitmapSourceWidth *
        VerticalImageEnMView1.CheckedCount;
      // Set the ImageEnView IEBitmap height
      ImageEnView1.IEBitmap.Height := iBitmapSourceHeight;
      { Initialize iCheckedCounter value so we know where to draw the checked image }
      iCheckedCounter := -1;
      // Get the checked images and draw them to the ImageEnView IEBitmap
      for i := 0 to VerticalImageEnMView1.ImageCount - 1 do
      begin
        if VerticalImageEnMView1.Checked[i] then
        begin
          { Set the iCheckedCounter value }
          Inc(iCheckedCounter);
          // Load input file
          VerticalImageEnMView1.CopyToIEBitmap(i, iIEBitmapSource);
          // Resize iIEBitmapSource
          iIEBitmapSource.Resample(iBitmapSourceWidth, -1);
          // Draw Source bitmap to ImageEnView Bitmap at the position of the
          // iBitmapSourceWidth * iCheckedCounter Value
          iIEBitmapSource.DrawToTIEBitmap(ImageEnView1.IEBitmap,
            iBitmapSourceWidth * iCheckedCounter, 0);
        end;
      end;
      // Update after drawing
      ImageEnView1.Update;
      // Free the iIEBitmapSource
    finally
      iIEBitmapSource.Free;
    end;
  finally
    Screen.Cursor := crDefault;
  end;
end;

uses imageenview, iemio, imageenproc, ieview, iemview, iexBitmaps, hyiedefs, hyieutils;
procedure TForm1.DrawHorzontally1Click(Sender: TObject);
var
  i: Integer;
  iIndex: Integer;
  iIEBitmapSource: TIEBitmap;
  iCheckedCounter: Integer;
  iBitmapSourceWidth: Integer;
  iBitmapSourceHeight: Integer;
begin
  Screen.Cursor := crHourGlass;
  try
    ImageEnView1.Clear;
    // Create a TIEbitmap to hold the source image
    iIEBitmapSource := TIEBitmap.Create;
    try
      iBitmapSourceWidth := 1024;
      iBitmapSourceHeight := 768;
      // Set the ImageEnView IEBitmap width to iBitmapSourceWidth * the number of checked images
      ImageEnView1.IEBitmap.Width := iBitmapSourceWidth *
        VerticalImageEnMView1.CheckedCount;
      // Set the ImageEnView IEBitmap height
      ImageEnView1.IEBitmap.Height := iBitmapSourceHeight;
      { Initialize iCheckedCounter value so we know where to draw the checked image }
      iCheckedCounter := -1;
      // Get the checked images and draw them to the ImageEnView IEBitmap
      for i := 0 to VerticalImageEnMView1.ImageCount - 1 do
      begin
        if VerticalImageEnMView1.Checked[i] then
        begin
          { Set the iCheckedCounter value }
          Inc(iCheckedCounter);
          // Load input file
          VerticalImageEnMView1.CopyToIEBitmap(i, iIEBitmapSource);
          // Resize iIEBitmapSource
          iIEBitmapSource.Resample(iBitmapSourceWidth, iBitmapSourceHeight,
            rfNone, True);
          // Draw Source bitmap to ImageEnView Bitmap at the position of the
          // iBitmapSourceHeight * iCheckedCounter Value
          iIEBitmapSource.DrawToTIEBitmap(ImageEnView1.IEBitmap,
            iBitmapSourceHeight * iCheckedCounter, 0);
        end;
      end;
      // Update after drawing
      ImageEnView1.Update;
      // Free the iIEBitmapSource
    finally
      iIEBitmapSource.Free;
    end;
  finally
    Screen.Cursor := crDefault;
  end;
end;