procedure TForm1.ImageEnView1DrawBackBuffer(Sender: TObject);
{ Draw an ellipse in the DrawBackBuffer Event - refresh with Update. }
var
  i: Double;
  z: Double;
  mx1: Double;
  my1: Double;
  lx1: Double;
  ly1: Double;
  x1, y1, x2, y2: Integer;
  bx, by: Integer;
begin
  bx := ImageEnView1.Layers[ImageEnView1.LayersCurrent].ConvXScr2Bmp
    (ABackBufferX);
  by := ImageEnView1.Layers[ImageEnView1.LayersCurrent].ConvYScr2Bmp
    (ABackBufferY);
  if (bx >= 0) and (bx <= ImageEnView1.IEBitmap.Width - 1) and (by >= 0) and
    (by <= ImageEnView1.IEBitmap.Height - 1) then
        with ImageEnView1.BackBuffer.Canvas do
        begin
          i := BrushPaint1.BrushSize / 2;
          Pen.Mode := pmNOTXOR; // pmCopy;
          Brush.Style := bsClear;
          z := ImageEnView1.Zoom / 100;
          mx1 := ABackBufferX; ( integer set in OnMouseMoveEvent }
          my1 := ABackBufferY; ( integer set in OnMouseMoveEvent } 
          lx1 := ABackBufferX;
          ly1 := ABackBufferY;
          x1 := Round(mx1 - i * z);
          y1 := Round(my1 - i * z);
          x2 := Round(lx1 + i * z);
          y2 := Round(ly1 + i * z);
          {if ImageEnView1.Bitmap.Width > 64 then
            Ellipse(x1, y1, x2, y2)
          else
            Rectangle(x1, y1, x2, y2);}
          // Draw crosshairs here
          Pen.Style := psDash;
          Pen.Width := 2;
          MoveTo(x1, y1);
          LineTo(x1 + 5, y1 + 5);
        end;
      end;
end;