void ChanVar (WinSize, r0,c0, Ch0,Ch1,Ch2, m0,m1,m2, v0,v1,v2)
int   WinSize, r0,c0;
BYTE  ** Ch0;
BYTE  ** Ch1;
BYTE  ** Ch2;
float m0,m1,m2;
float *v0,*v1,*v2;
{
   int    r,c,N;
   float  d0,d1,d2;

   N = WinSize*WinSize;
   *v0 = *v1 = *v2 = (float)0;
   for (r=r0; r<r0+WinSize; r++)  {
      for (c=c0; c<c0+WinSize; c++)  {
         d0 = Ch0 [r][c] - (float)m0;   *v0 += d0*d0;
         d1 = Ch1 [r][c] - (float)m1;   *v1 += d1*d1;
         d2 = Ch2 [r][c] - (float)m2;   *v2 += d2*d2;
   }  }
   *v0 /= N-1;
   *v1 /= N-1;
   *v2 /= N-1;
}
