/*--------------------------- MegaWave2 module  -----------------------------*//* mwcommand name = {heat}; author = {"Lionel Moisan"}; version = {"1.1"}; function = {"Heat Equation (finite differences scheme with 4 neighbors)"}; usage = {           'n':[n=10]->n     "number of iterations (default: 10)",           's':[s=0.1]->s    "time step (default: 0.1), can be negative",	   in->in            "input image",	   out<-heat         "output image"};*//*--------------------------------------------------------------------------*/#include <stdio.h>#include "mw.h"/*--- One iteration of u<-u+s*Laplacian ---*/void iter(u,v,s)Fimage u,v;float  s;{  int   i,j,im,i1,jm,j1;  float laplacian;  for (i=0;i<u->ncol;i++) for (j=0;j<u->nrow;j++) {    if (j==0) jm=1; else jm=j-1;    if (j==u->nrow-1) j1=u->nrow-2; else j1=j+1;    if (i==0) im=1; else im=i-1;    if (i==u->ncol-1) i1=u->ncol-2; else i1=i+1;    laplacian =       - 4.0  * u->gray[u->ncol * j  + i ]             + u->gray[u->ncol * j  + im]             + u->gray[u->ncol * j  + i1]             + u->gray[u->ncol * jm + i]             + u->gray[u->ncol * j1 + i];    v->gray[ v->ncol*j+i ] = u->gray[ u->ncol*j+i ] + s * laplacian;  }}/*--- WARNING : the original image (in) is destroyed by this module -----*/Fimage heat(in,n,s)Fimage in;int    *n;float  *s;{  Fimage u,*old,*new,*tmp;  int    i;  u = mw_change_fimage(NULL,in->nrow,in->ncol);  if (!u) mwerror(FATAL,1,"heat: not enough memory");  old = &in;  new = &u;  for (i=*n;i--;) {    iter(*old,*new,*s);    tmp=old; old=new; new=tmp;  }    if (*old == in) mw_copy_fimage(in,u);  mw_delete_fimage(in);  return u;}