Как правильно рисовать на канве?

void draw()
{
    BASS_ChannelGetData(stream,fft,BASS_DATA_FFT512);
    int i,YPos ,X = 20, Y = 25;
    Single YVal;
    if(FrmClear)
       Form1->PaintBox1->Repaint();
    for(i = 0; i<120;i++)
    {
        YVal = fft[i + 5];
        YPos = YVal * 500;
        if(YPos > Form1->PaintBox1->Height)
            YPos = 44;
        if(YPos >= FFTPeacks[i])
            FFTPeacks[i] = YPos;
        else
            FFTPeacks[i] = FFTPeacks[i] - 1;
 
        if(YPos >= FFTFallOff[i])
            FFTFallOff[i] = YPos;
        else
            FFTFallOff[i] = FFTFallOff[i] - 3;
        if ((Form1->PaintBox1->Height - FFTPeacks[i]) > Form1->PaintBox1->Height)
            FFTPeacks[i] = 0;
        if ((Form1->PaintBox1->Height - FFTFallOff[i]) > Form1->PaintBox1->Height)
            FFTFallOff[i] = 0;
        GradientFillCanvas(Form1->PaintBox1->Canvas,RGB(251, 0, 0), RGB(255, 224, 4),
                                       Rect(i * (ColWidth + 1),Form1->PaintBox1->Height - FFTFallOff[i],i * (ColWidth + 1) + ColWidth,Form1->PaintBox1->Height), gdVertical);
    }
    Form1->PaintBox1->Canvas->Draw(0,0,Form1->Image24->Picture->Bitmap);
    BitBlt(Form1->PaintBox1->Canvas->Handle, 0,0, Form1->PaintBox1->Width, Form1->PaintBox1->Height, Form1->PaintBox1->Canvas->Handle, 0, 0, SRCCOPY);
}

PaintBox1onpaint()
{
Draw();
}

TimerTimer()
{
  PaintBox1->refresh();
}

Image1Click()
{
   if(Image1->Tag ==0)
   {
         ImageList1->Draw(Image1->Canvas,0,0,0);
     Image1->Repaint();
     Image1->Tag = 1;
   }
   else
   {
        ImageList1->Draw(Image1->Canvas,0,0,3);
     Image1->Repaint();
     Image1->Tag = 0;
   }
}