Delphi绘图功能[3] —— 使用Polyline、Polygon绘制多边形、System.Sin、System.Cos函数画圆 — 绘制五环图标

procedure TForm1.FormCreate(Sender: TObject);
begin
  Canvas.Pen.Width := 4;
  Canvas.Pen.Color := clRed;
  Canvas.Brush.Color := clYellow;   //设置画刷颜色
end;

{绘制多边形：它的参数是一个点数组，这里定义了一个常数数组}
procedure TForm1.Button7Click(Sender: TObject);
const
  pts:array[0..3] of TPoint = (
    (x:10; y:40),
    (x:46; y:120),
    (x:82; y:40),
    (x:46; y:10)
  );
begin
  Canvas.Polygon(pts);
end;

{绘制连续的一组直线; 它的参数也是一个点数组, 我只是把上面的平移了一点}
procedure TForm1.Button8Click(Sender: TObject);
const
  pts:array[0..3] of TPoint = (
    (x:10+82; y:40),
    (x:46+82; y:120),
    (x:82+82; y:40),
    (x:46+82; y:10)
  );
begin
  Canvas.Polyline(pts);
end;

const    {把五环颜色定义为常量数组}
  Colors:array[0..4] of TColor = (clBlue,clBlack,clRed,clYellow,clGreen);
var
  ci:Integer;   {用作颜色序号}

procedure TForm1.FormCreate(Sender: TObject);
begin
  Button9.Caption := '重绘';
  Self.Color := clWhite;
  Canvas.Pen.Width:=5;
end;

procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
const
  r = 30;  {圆半径}
var
  radian: Double; {记录弧度：Sin、Cos函数需要弧度做参数；弧度 = 角度 * Pi/180}
  i,a,b :Integer;
begin
  Canvas.MoveTo(X,Y - r);
  Canvas.Pen.Color := Colors[ci];
  for i := 1 to 360 do
  begin
    radian := i * (Pi/180);          {获取弧度}
    a := X + Round(Sin(radian) * r); {用 Sin 函数获取横坐标}
    b := Y - Round(Cos(radian) * r); {用 Cos 函数获取纵坐标}
    Canvas.LineTo(a, b);             {绘制}
    Application.ProcessMessages;     {不要影响其他操作}
    Sleep(3);                        {等 3 毫秒}
  end;
  Inc(ci);
  if ci = 5 then ci := 0;
end;

procedure TForm1.Button9Click(Sender: TObject);
begin
   ci :=0 ;
   Repaint;//重画
end;