В чём ошибка? Char выводит нормальный график, а Image не понятно что

//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
  double a,b,h,ymin1,ymax1,ymin2,ymax2,pi=3.14;
  int n;
  double fun1(double);
  double fun2(double);
 
__fastcall TForm1::TForm1(TComponent* Owner):TForm(Owner)
{}
void __fastcall TForm1::FormCreate(TObject *Sender)
{
        Edit1->Text="-6";
        Edit2->Text="6";
        Edit3->Text="50";
}
void __fastcall TForm1::Button1Click(TObject *Sender)
{
double x, r1,r2;
a=StrToFloat(Edit1->Text);
b=StrToFloat(Edit2->Text);
n=StrToInt(Edit3->Text);
h=(b-a)/n;
Edit4->Text=FloatToStr(h);
ymin1 = ymax1= fun1(a);
ymin1 = ymax2= fun2(a);
for (x = a+h; x<=b; x+=h) {
                r1 = fun1(x);
                r2 = fun2(x);
                if(ymin1>r1) ymin1 = r1;
                if(ymax1<r1) ymax1 = r1;
                if(ymin1>r2) ymin1 = r2;
                if(ymax2<r2) ymax2 = r2;
                int xmax, ymax, xt, yt, y0, x0;
double hx,hy,x;
Chart1->Series[0]->Clear();
for(double x=a; x<=b; x+=h)
      Chart1->Series[0]->AddXY(x,fun1(x));
  Image1->Canvas->Pen->Color=clBlack;
 xmax = Image1->Width;        ymax = Image1->Height;
  Image1->Canvas->Rectangle(0,0,xmax,ymax);
  y0=ymax/2;      x0=xmax/2;
  Image1->Canvas->MoveTo(0,y0);
  Image1->Canvas->LineTo(xmax,y0);
  Image1->Canvas->MoveTo(x0,0);
  Image1->Canvas->LineTo(x0,ymax);
  Image1->Canvas->Pen->Color=clRed;
  Image1->Canvas->Pen->Width=2;
hx=(b-a)/xmax;    hy=(ymax2-ymin2)/ymax;
Image1->Canvas->MoveTo(ceil(x0+a/hx),ceil(y0-fun2(a)/hy));
for(x=a; x<=b; x+=h)
   Image1->Canvas->LineTo(ceil(x0+x/hx),ceil(y0-fun2(x)/hy)); }
}
 
 double fun1(double r1) {
 int k,s1=0;
 for(k=1;k<n;k++){
 s1=s1+(pow(r1,k)*cos((k*pi)/3))/k;
  }
  return s1;
 }
 double fun2(double r2) {
  double m;
  m= -1/2.*log(1-2*r2*cos(pi/3)+pow(r2,2));
        return m;
  }