请教下如何画圆啊？在线等！！

Question

要求是就是鼠标开始下压的那个点为圆心坐标，移动后的点为圆上的一个点，半径就是这两个点的距离！
谢谢了！

Answer 1

unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs,jpeg,ExtCtrls, StdCtrls;type
  TForm1 = class(TForm)
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
  private
    fselecting:boolean;
    fbeginpt,fendpt:tpoint;
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  fselecting:=true;
  fbeginpt:=Form1.ScreenToClient(mouse.CursorPos);
end;
procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  fselecting:=false;
  fendpt:=Form1.ScreenToClient(mouse.CursorPos);
  Self.Repaint;
end;
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
 fendpt:=Form1.ScreenToClient(mouse.CursorPos);
 if fselecting then
 begin
   Canvas.FillRect(Canvas.ClipRect);
   //Canvas.Rectangle(rect(fbeginpt,fendpt));
   canvas.Ellipse(rect(fbeginpt,fendpt));
   canvas.Pen.Color:=clred;
   Canvas.Pen.Width:=1;
 end;
end;end.

Answer 2

用控件 托拽就可以了 就这么简单
用visual graph来做