delphi - LineDDA を使用した EllipsePoints

Question

GDI Canvas Ellipse でグリップ ポイントを描画できますが、2 番目のポイントが正しく描画されません。示された効果をどのように防止しますか?

procedure TFormMain.DrawMarchingAnts;
var
  iWidth: integer;
begin
  AMarchingAntsCounter := AMarchingAntsCounterStart;
  // Use LineDDA to draw each of the 4 edges of the rectangle
  LineDDA(AMarchingAntsPointA.X, AMarchingAntsPointA.Y, AMarchingAntsPointB.X, AMarchingAntsPointA.Y,
    @MarchingAnts, LongInt(
    AMarchingAntsCanvas));
  LineDDA(AMarchingAntsPointB.X, AMarchingAntsPointA.Y, AMarchingAntsPointB.X, AMarchingAntsPointB.Y,
    @MarchingAnts, LongInt(
    AMarchingAntsCanvas));
  LineDDA(AMarchingAntsPointB.X, AMarchingAntsPointB.Y, AMarchingAntsPointA.X, AMarchingAntsPointB.Y,
    @MarchingAnts, LongInt(
    AMarchingAntsCanvas));
  LineDDA(AMarchingAntsPointA.X, AMarchingAntsPointB.Y, AMarchingAntsPointA.X, AMarchingAntsPointA.Y,
    @MarchingAnts, LongInt(
    AMarchingAntsCanvas));
  if AMarchingAntsPointB.X > AMarchingAntsPointA.X then
    ARubberbandVisible := True
  else
    ARubberbandVisible := False;
  AMarchingAntsCanvas.Pen.Width := 1;
  AMarchingAntsCanvas.Pen.Color := clWhite;
  AMarchingAntsCanvas.Brush.Color := clRed;
  AMarchingAntsCanvas.Ellipse(AMarchingAntsPointA.X-4, AMarchingAntsPointA.Y-4, AMarchingAntsPointA.X+4, AMarchingAntsPointA.Y+4);
  iWidth := AMarchingAntsPointB.X - AMarchingAntsPointA.X;
  AMarchingAntsCanvas.Ellipse(AMarchingAntsPointA.X-4 + iWidth, AMarchingAntsPointA.Y-4, AMarchingAntsPointA.X+4 + iWidth, AMarchingAntsPointA.Y+4);
end;