仿 Delphi 设计虚线背景

procedure TForm1.DrawBackground;
var FScale : integer;
   FGridX :double;
      FGridY :double;

  procedure Line(x, y, x1, y1: Integer);
  begin
    Canvas.MoveTo(x, y);
    Canvas.LineTo(x1, y1);
  end;

    function   ReverseColor(AColor:   TColor):   TColor;
    var
        iR0,   iR1,   iG0,   iG1,   iB0,   iB1:   integer;
    begin
        iR0   :=   GetRValue(AColor);
        iR1   :=   255   -   iR0;
        iG0   :=   GetGValue(AColor);
        iG1   :=   255   -   iG0;
        iB0   :=   GetBValue(AColor);
        iB1   :=   255   -   iB0; 

        Result   :=   RGB(iR1,   iG1,   iB1);
    end;


  procedure DrawPoints;
  var
    GridBmp: TBitmap;
    i: Extended;
    c: TColor;
    dx, dy: Extended;
  begin
      c := ReverseColor(self.Color);
      FScale := 1;
      FGridX :=       5; // 96 / 25.4
      FGridY :=       5; // 96 / 25.4
    dx := FGridX * FScale;
    dy := FGridY * FScale;
    if (dx > 2) and (dy > 2) then
    begin
      GridBmp := TBitmap.Create;
      GridBmp.Width:= Width;
      GridBmp.Height := 1;

      GridBmp.Canvas.Pen.Color := self.Color;
      GridBmp.Canvas.MoveTo(0, 0);
      GridBmp.Canvas.LineTo(Width, 0);

      i := 0;
      while i < Width do
      begin
        GridBmp.Canvas.Pixels[Round(i), 0] := c;
        i := i + dx;
      end;

      i := 0;
      while i < Height do
      begin
        Canvas.Draw(0, Round(i), GridBmp);
        i := i + dy;
      end;

      GridBmp.Free;
    end;
  end;
begin
        DrawPoints;
end;