Избавиться от мигания при рисовании

int spiral_angle=0,spiral_col=0;
bool spiral_recol=false;
void __fastcall TForm1::spiralTimer(TObject *Sender)
{
pb->Canvas->Brush->Color=clBlack;
pb->Canvas->Rectangle(0,0,Width,Height);
int i;
double ro,k=7,fi,step=0.1;
int W,H,x,y;
W=Form1->ClientWidth/2;
H=Form1->ClientHeight/2;
if (spiral_recol==true)spiral_col++;
if (spiral_recol==false)spiral_col--;
if (spiral_col>=254)spiral_recol=false;
if (spiral_col<=1)spiral_recol=true;
x=k*fi*W;
y=H;
pb->Canvas->Pen->Color=TColor(RGB(spiral_col,-spiral_col,spiral_col));
pb->Canvas->Pen->Width=5;
pb->Canvas->MoveTo(Width/2,Height/2);
spiral_angle++;
for(i=0;i<1500;i++)
        {
        fi=i*step;
        x=k*fi*cos(fi+spiral_angle)+W;
        y=k*fi*sin(fi+spiral_angle)+H;
        pb->Canvas->LineTo(x,y);
        }
pb->Canvas->Pen->Color=clBlack;pb->Canvas->Brush->Color=clBlack; pb->Canvas->Pen->Width=1;
}

__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
DoubleBuffered=true;
}
 
//сдесь ;)

void __fastcall TForm1::EffectStrobe(int pause=50,bool randcolor=true,TColor cl=clBlack)
{
if (randcolor==true)pb->Canvas->Brush->Color=TColor(RGB(random(255),random(255),random(255)));
else pb->Canvas->Brush->Color=cl;
pb->Canvas->Rectangle(0,0,pb->Width,pb->Height);
Sleep(pause);
pb->Canvas->Brush->Color=clBlack;
pb->Canvas->Rectangle(0,0,Width,Height);
}

void __fastcall TForm1::FormResize(TObject *Sender)
{
pb->Left=0;
pb->Top=0;
pb->Width=ClientWidth;
pb->Height=ClientHeight;
}