// Enlarge the selection by ten pixels on all sides
With ImageEnView1 do
begin
  SelectionBase := iesbBitmap;
  Select( SelX1 - 10, SelY1 - 10, SelX2 - 10, SelY2 - 10 );
End;

procedure ScalePoint(var APoint: TPoint; AHorzontalScale, AVerticalScale: extended; AOrigin: TPoint);
var
  iLeft, iTop: Integer;
begin
  iLeft := APoint.X - AOrigin.X;
  iTop := APoint.Y - AOrigin.Y;
  APoint := Point(Round(iLeft * AHorzontalScale) + AOrigin.X, Round(iTop * AVerticalScale) + AOrigin.Y);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  i: Integer;
  iPoint: TPoint;
  iPointCount: Integer;
  iPoints: Array of TPoint;
begin
  ImageEnView1.LockPaint;
  iPointCount := ImageEnView1.PolySelCount;
  SetLength(iPoints, iPointCount);
  for i := 0 to iPointCount - 1 do
  begin
    iPoint := ImageEnView1.PolySel[i];
    ScalePoint(iPoint, 1.1, 1.1, ImageEnView1.PolySel[0]);
    iPoints[i].X := iPoint.X;
    iPoints[i].Y := iPoint.Y;
  end;
  ImageEnView1.DeSelect;
  for i := 0 to iPointCount - 1 do
    ImageEnView1.AddSelPoint(iPoints[i].X, iPoints[i].Y);
  ImageEnView1.UnLockPaint;
end;

paintView->SelectionMaskDepth = 8; //set after image is loaded


// enlarge selection area using feathering (blur) with radius 4:
paintView->MakeSelectionFeather(4);
// set feathering to 0 - selection area will stay enlarged
paintView->MakeSelectionFeather(0);
// update all pixels inside mask to highest value (correct pixels < 255)
for (int i = 0; i < paintView->Height; i++)
   {
   for (int j = 0; j < paintView->Width; j++)
       {
	if (paintView->SelectionMask->IsPointInside(j, i))
	   paintView->SelectionMask->SetPixel(j, i, 255);
       }
   }