使用 System.Sin、System.Cos 函数画圆 - 绘制五环图标

本例效果图:

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    procedure FormCreate(Sender: TObject);

    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;

      Shift: TShiftState; X, Y: Integer);

    procedure Button1Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



const {把五环的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

  Button1.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.Button1Click(Sender: TObject);

begin

  ci := 0;

  Repaint;

end;



end.


 
   

System 单元下的公用函数目录

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