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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