void Ellipse (HDC hdc,int xc, int yc, int enx, int eny,BYTE red,BYTE gre,BYTE blu)
{
  int x,y;
  double k;
  long a2,b2,dds,ddt,t,s,e,ca,cd,indx,dxt;
  int a,b;
  a=abs(enx-xc);
  b=abs(eny-yc);
  a2=(long)a*(long)a;
  b2=(long)b*(long)b;

  dds=4*a2;
  ddt=4*b2;
  dxt=(float)a2/sqrt(a2+b2);
  t=0;
  s=-4*a2*b;
  e=(-s/2)-2*b2-a2;
  ca=-6*b2;
  cd=ca-4*a2;
  x=xc;
  y=yc+b;
  SetPixel(hdc,x,y,0);
  SetPixel(hdc,x,2*yc-y,0);
  SetPixel(hdc,2*xc-x,2*yc-y,0);
  SetPixel(hdc,2*xc-x,y,0);
  for(indx=1;indx<=dxt;indx++)
  {
    x++;
    if(e>=0)e+=t+ca;
    else 
    {
      y--;
      e+=t-s+cd;
      s+=dds;
    }
    t-=ddt;
  SetPixel(hdc,x,y,0);
  SetPixel(hdc,x,2*yc-y,0);
  SetPixel(hdc,2*xc-x,2*yc-y,0);
  SetPixel(hdc,2*xc-x,y,0);
  }
  dxt=abs(y-yc);
  e-=t/2+s/2+b2+a2;
  ca=-6*a2;
  cd=ca-4*b2;
  for(indx=1;indx<=dxt;indx++)
  {
    y--;
    if(e<=0) e+=-s+ca;
    else 
    {
      x++;
      e+=-s+t+cd;
      t-=ddt;
    }
    s+=dds;
    SetPixel(hdc,x,y,0);
    SetPixel(hdc,x,2*yc-y,0);
    SetPixel(hdc,2*xc-x,2*yc-y,0);
    SetPixel(hdc,2*xc-x,y,0);
  }
}