procedure TForm1.FormPaint(Sender: TObject); var x: Integer; y,a: Double; begin Canvas.Pen.Width:=3; Canvas.MoveTo(0,Trunc(self.ClientHeight/2)); for x := 0 to self.ClientWidth do begin a := (x/self.ClientWidth) * 2 * Pi; y := Sin(a); y := (1-y)*self.ClientHeight/2; Canvas.LineTo(Trunc(x), Trunc(y)); end; end; 程序首先设置了窗体的Canvas对象中画笔的宽度,并且把绘图的起点移动到了窗体中(0,Trunc(self.ClientHeight/2))的位置。然后通过一个循环中的a:= (x/self.ClientWidth)*2*Pi语句将一个正弦周期内的角度值转换为弧度值,并且把正弦计算后的结果存储在变量y中。最后,循环中的Canvas.LineTo(Trunc(x), Trunc(y))语句就会在窗体上绘制出连续的正弦曲线。
type TForm1 = class(TForm) procedure FormPaint(Sender: TObject); procedure FormResize(Sender: TObject); procedure FormCreate(Sender: TObject); private { Private declarations } public { Public declarations } end;
var Form1: TForm1; implementation {$R *.dfm} procedure TForm1.FormPaint(Sender: TObject); var x: Integer; y,a: Double; begin Canvas.Pen.Width:=3; Canvas.MoveTo(0,Trunc(self.ClientHeight/2)); for x := 0 to self.ClientWidth do begin a := (x/self.ClientWidth) * 2 * Pi; y := Sin(a); y := (1-y)*self.ClientHeight/2; Canvas.LineTo(Trunc(x), Trunc(y)); end; end;
procedure TForm1.FormResize(Sender: TObject); begin Refresh; end;
procedure TForm1.FormCreate(Sender: TObject); begin self.DoubleBuffered:=true; //防止图形闪烁 end; end. 保存文件,然后按F9键运行程序。在程序运行过程中,会自动在窗体上绘制正弦曲线,运行结果如图1所示。