/*--------------------------- Commande MegaWave -----------------------------*//* mwcommandname = {fvar};author = {"Jacques Froment"};function = {"Compute the variance of the gray level of an image"};usage = {A->A "input fimage",v<-fvar "output variance"};version = {"1.1"};*/#include <stdio.h>#include  "mw.h"float fvar(A)Fimage A;{  int s;  register float *ptr;  register int i;  double m,v,vr;  s = A->ncol*A->nrow;  if (s <= 1) return(0.);  for (m=0., i=0, ptr = A->gray; i<s; i++,ptr++) m += *ptr;  m /= (double)s;        vr = 0.0;  for (i=0, ptr = A->gray;i<s;i++,ptr++)     {      v = *ptr - m;        vr += v*v;    }  vr /=  (double)s - 1.;  return((float) vr);}