// Load an image, set center 50% to negative and save
myBitmap := TIEBitmap.Create();
myBitmap.Read( 'D:\Image.jpg' );
with TImageEnProc.CreateFromBitmap( myBitmap ) do
begin
  // Select center area of image
  SelectedRect := Rect( MulDiv( 25, myBitmap.Width, 100 ),
                        MulDiv( 25, myBitmap.Height, 100 ),
                        MulDiv( 75, myBitmap.Width, 100 ),
                        MulDiv( 75, myBitmap.Height, 100 ));
  Selected := True;
  Negative();
  Free;
end;
myBitmap.Write( 'D:\Image_Out.jpg' );
myBitmap.Free;