Delphi实例之绘制正弦函数图像

                       Delphi实例之绘制正弦函数图像

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, ExtCtrls;

type
  TForm1 = class(TForm)
    Image1: TImage;
    Button1: TButton;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Label5: TLabel;
    Label6: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  x,l:Integer;
  y,a:double;
begin
  Image1.Picture.Bitmap:=TBitMap.Create;
  Image1.Picture.Bitmap.Width:=Image1.Width;       
  Image1.Picture.Bitmap.Height:=Image1.Height;
  l:=Image1.Picture.Bitmap.Width;
     {下面的语句用于绘制直角坐标系}
  Image1.Canvas.MoveTo(0,(Image1.Height div 2));
  Image1.Canvas.Pen.Color:=clBlue;
  Image1.Canvas.LineTo(Image1.Width,(Image1.Height div 2));{绘制函数图像X轴}
  Image1.Canvas.MoveTo((Image1.Width div 2),Image1.Height);
  Image1.Canvas.LineTo((Image1.Width div 2),0);{绘制函数图像Y轴}
  for x:=0 to l do
    begin
      a:=(x/l)*2*Pi;{角度化弧度}
      y:=sin(2*a);{为了加强美观效果，这里讲振幅设为2}
      y:=y*(Image1.Picture.Bitmap.Height/2);
      y:=y+(Image1.Picture.Bitmap.Height/2);
      Image1.Picture.Bitmap.Canvas.Brush.Style:=bsSolid;
      Image1.Picture.Bitmap.Canvas.Pixels[Trunc(x),Trunc(y)]:=clRed;{当然也可以用LineTo过程来实现，但是要注意设置Pen.Width到合适的值}
    end;
  label1.Visible:=true;
  Label2.Visible:=true;
  label3.Visible:=true;
  Label4.Visible:=true;
  label5.Visible:=true;
  Label6.Visible:=true;
end;

end.

注意，这里我用了四个标签，分别用于显示X,Y,0,f(x)=sinx，并事先将它们的Visible属性设为False，当图像绘制完成后在将Visible改为True。