请问怎么样可以画一个可随着半径变化而改变的圆？共200分（含BCB论坛的100分）

Question

http://expert.csdn.net/Expert/topic/1265/1265466.xml?temp=.6246607含有100分送上，共200分
我想画一个圆，可以随着半径变化而不断变化的圆，
我的代码如下：
void __fastcall TForm1::Image1MouseMove(TObject *Sender, TShiftState Shift,
      int X, int Y)
{
        if(menuCRCircle->Checked && Drawing){
                Image1->Canvas->Pen->Mode=pmNotXor;
                Image1->Canvas->MoveTo(points[0].x,points[0].y);
                Image1->Canvas->LineTo(points[1].x,points[1].y);
                points[1].x=X;
                points[1].y=Y;
                float R;
                R=sqrt((points[0].x-points[1].x)*(points[0].x-points[1].x)+ (points[0].y-points[1].y)*(points[0].y-points[1].y));
                Image1->Canvas->Ellipse(points[0].x-R,points[0].y+R,points[0].x+R,points[0].y-R);
                Image1->Canvas->MoveTo(points[0].x,points[0].y);
                Image1->Canvas->LineTo(points[1].x,points[1].y);
        }
//points[0]为圆心,points[1]圆上一点我画好后，不是我想要的结果，就是说不是橡皮条的效果，急
}

Answer 1

给你一个Delphi的，我就不给你翻译了。
是画矩形的，和画圆也差不多
unit draw;interfaceuses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  ExtCtrls;type
  TForm1 = class(TForm)
    procedure FormMouseDown(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
      Y: Integer);
    procedure FormMouseUp(Sender: TObject; Button: TMouseButton;
      Shift: TShiftState; X, Y: Integer);
  private
    p1,p2:TPoint;
  public
    { Public declarations }
  end;var
  Form1: TForm1;
  lastx,lasty:integer;
implementation{$R *.DFM}procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  P1.x:=x;
  P1.y:=y;
  p2:=p1;
  canvas.pen.Mode:=pmNot;
  canvas.pen.Color:=clblack;
  canvas.brush.Style:=bsclear;
end;procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
  Y: Integer);
begin
   if (shift=[ssleft]) then begin
      canvas.Rectangle(p1.x,p1.y,p2.x,p2.y);  //擦除
      canvas.Rectangle(p1.x,p1.y,x,y);        //重画
      p2.x:=x;
      p2.y:=y;
   end;end;procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
begin
  canvas.Rectangle(p1.x,p1.y,p2.x,p2.y);   //擦除}
end;end.

Answer 2

procedure TForm1.tttt(Ax, Ay, AR: integer);
begin
  Form1.Canvas.RoundRect(Ax - Ar,Ay,Ax,Ay + AR,Ax + AR,Ay);
end;

Answer 3

哦上面错了
procedure tttt(Ax,Ay,AR:integer);procedure TForm1.tttt(Ax, Ay, AR: integer);
begin
  Form1.Canvas.Ellipse(Ax - Ar,Ay - AR,Ax + AR,Ay + AR);
end;