Delphi的绘图功能[3]

unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls;
type
　TForm1 = class(TForm)
　　Button1: TButton;
　　Button2: TButton;
　　Button3: TButton;
　　Button4: TButton;
　　Button5: TButton;
　　procedure FormCreate(Sender: TObject);
　　procedure Button1Click(Sender: TObject);
　　procedure Button2Click(Sender: TObject);
　　procedure Button3Click(Sender: TObject);
　　procedure Button4Click(Sender: TObject);
　　procedure Button5Click(Sender: TObject);
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
var
　btn: TButton;
const
　y1 = 10;
　y2 = 80;

{先设置画笔画刷}procedure TForm1.FormCreate(Sender: TObject);
begin
　Canvas.Pen.Width := 4;
　Canvas.Pen.Color := clRed;
　Canvas.Brush.Color := clWhite;
end;{给出左上角和右下角的坐标就可以绘制矩形}procedure TForm1.Button1Click(Sender: TObject);
begin
　btn := TButton(Sender);
　Canvas.Rectangle(btn.Left, y1, btn.Left+btn.Width, y2);
end;{给出一个矩形结构做参数也可以绘制矩形}procedure TForm1.Button2Click(Sender: TObject);
var
　R: TRect; {定义一个矩形结构}
begin
　btn := TButton(Sender);
　R := Rect(btn.Left, y1, btn.Left+btn.Width, y2);
　Canvas.Rectangle(R);
end;