/*-------------------------------------------------------------------

  File        : image_registration.cpp

  Description : Compute a motion field between two images, 
                with a multiscale and variational algorithm

  Author      : David Tschumperlé
  
  This software is governed by the CeCILL  license under French law and
  abiding by the rules of distribution of free software.  You can  use, 
  modify and/ or redistribute the software under the terms of the CeCILL
  license as circulated by CEA, CNRS and INRIA at the following URL
  "http://www.cecill.info". 
  
  As a counterpart to the access to the source code and  rights to copy,
  modify and redistribute granted by the license, users are provided only
  with a limited warranty  and the software's author,  the holder of the
  economic rights,  and the successive licensors  have only  limited
  liability. 
  
  In this respect, the user's attention is drawn to the risks associated
  with loading,  using,  modifying and/or developing or reproducing the
  software by the user in light of its specific status of free software,
  that may mean  that it is complicated to manipulate,  and  that  also
  therefore means  that it is reserved for developers  and  experienced
  professionals having in-depth computer knowledge. Users are therefore
  encouraged to load and test the software's suitability as regards their
  requirements in conditions enabling the security of their systems and/or 
  data to be ensured and,  more generally, to use and operate it in the 
  same conditions as regards security. 
  
  The fact that you are presently reading this means that you have had
  knowledge of the CeCILL license and that you accept its terms.

  -----------------------------------------------------------------*/

#include "../CImg.h"
// The lines below are not necessary in your own code, it simply allows 
// the source compilation with compilers that do not respect the C++ standart.
#if ( defined(_MSC_VER) && _MSC_VER<=1200 ) || defined(__DMC__)
#define std
#endif
using namespace cimg_library;

// animate_warp() : Create warping animation from two images and a motion field
//----------------
void animate_warp(const CImg<unsigned char>& src, const CImg<unsigned char>& dest, const CImg<>& u,
                  const bool morph, const bool imode,
                  const char *filename,int nb,CImgDisplay *disp) {
  CImg<unsigned char> visu = CImgl<unsigned char>(src,dest,src).get_append('x'), warp(src,false);
  float t=0;
  for (unsigned int iter=0; !disp || (!disp->closed && disp->key!=cimg::keyQ); iter++) {
    if (morph) cimg_mapXYV(warp,x,y,k) {
      const float dx = u(x,y,0), dy = u(x,y,1), 
        I1 = (float)src.linear_pix2d(x-t*dx, y-t*dy, k),
        I2 = (float)dest.linear_pix2d(x+(1-t)*dx,y+(1-t)*dy,k);
      warp(x,y,k) = (unsigned char)((1-t)*I1 + t*I2);
    } else cimg_mapXYV(warp,x,y,k) {
      const float dx = u(x,y,0), dy = u(x,y,1), I1 = (float)src.linear_pix2d(x-t*dx, y-t*dy, 0,k);
      warp(x,y,k) = (unsigned char)I1;
    }
    if (disp) visu.draw_image(warp,2*src.width,0).display(disp->resize()).wait(30);
    if (filename && *filename && (imode || (int)iter<nb)) {
      std::fprintf(stderr,"\r  > frame %d           ",iter);
      warp.save(filename,iter); 
    }
    iter++;
    t+=1.0f/nb;
    if (t<0) { t=0; nb=-nb; }
    if (t>1) { t=1; nb=-nb; if (filename && *filename) exit(0); }
  }
}

// get_warp() : Return the image src warped by the motion field u.
//------------
template<typename T> CImg<T> getwarp(const CImg<T>& src, const CImg<>& u) {
  CImg<T> warp(src);
  cimg_mapXY(warp,x,y) warp(x,y) = (T)src.linear_pix2d(x - u(x,y,0), y - u(x,y,1));
  return warp;
}


// optmonoflow() : Compute optical flow for one scale ( semi-implicite scheme ) between I2->I1
//---------------
CImg<> optmonoflow(const CImg<>& I1,const CImg<>& I2,const CImg<>& u0, 
                   const float smooth, const float precision,CImgDisplay *disp) {

  CImg<> u = u0.get_resize(I1.width,I1.height,1,2,3),dI(u);
  CImg_3x3(I,float);
  float dt=2,E=1e20f;

  // compute first derivatives of I2
  cimg_map3x3(I2,x,y,0,0,I) {
    dI(x,y,0) = 0.5f*(Inc-Ipc);
    dI(x,y,1) = 0.5f*(Icn-Icp);
  }

  // Main PDE iteration
  for (unsigned int iter=0; iter<100000; iter++) {
    std::fprintf(stderr,"\r- Iteration %d - E = %g",iter,E); fflush(stderr);
    const float Eold = E;
    E = 0;
    cimg_3mapXY(u,x,y) {
      const float 
        X = x + u(x,y,0),
        Y = y + u(x,y,1),
        deltaI = (float)(I2.linear_pix2d(X,Y) - I1(x,y));
      float tmpf = 0;
      cimg_mapV(u,k) {
        const float
          ux  = 0.5f*(u(_nx,y,k)-u(_px,y,k)),
          uy  = 0.5f*(u(x,_ny,k)-u(x,_py,k));
        u(x,y,k) = (float)( u(x,y,k) +
                            dt*(
                                -deltaI*dI.linear_pix2d(X,Y,k) +
                                smooth* ( u(_nx,y,k) + u(_px,y,k) + u(x,_ny,k) + u(x,_py,k) )
                                )
                            )/(1+4*smooth*dt);
        tmpf += ux*ux + uy*uy;
      }
      E += deltaI*deltaI + smooth * tmpf;
    }
    if (std::fabs(Eold-E)<precision) break;
    if (Eold<E) dt*=0.5;
    if (disp) disp->resize();
    if (disp && !(iter%50)) {
      const unsigned char white = 255;
      CImg<unsigned char> tmp = getwarp(I1,u).normalize(0,200);
      tmp.resize(disp->width,disp->height).draw_quiver(u,&white,15,-14,0,0.7f).display(*disp);
    }
  }
  return u;
}


// optflow() : multiscale version of the Horn&Schunk algorithm
//-----------
CImg<> optflow(const CImg<>& xsrc,const CImg<>& xdest,
               const float smooth,const float precision,const unsigned int pnb_scale,CImgDisplay *disp=NULL) {
  const CImg<>
    src  = xsrc.get_norm_pointwise(1).resize(xdest.width,xdest.height,1,1,3).normalize(0,1),
    dest = xdest.get_norm_pointwise(1).resize(xdest.width,xdest.height,1,1,3).normalize(0,1);
  CImg<> u = CImg<>(src.width,src.height,1,2).fill(0);

  const unsigned int nb_scale = pnb_scale>0?pnb_scale:(unsigned int)(2*std::log((double)(cimg::max(src.width,src.height))));
  for (int scale=nb_scale-1; scale>=0; scale--) {
    const CImg<> I1 = src.get_resize((int)(src.width/std::pow(1.5,scale)), (int)(src.height/std::pow(1.5,scale)) ,1,1,3);
    const CImg<> I2 = dest.get_resize((int)(src.width/std::pow(1.5,scale)), (int)(src.height/std::pow(1.5,scale)) ,1,1,3);
    std::fprintf(stderr," * Scale %d\n",scale);
    u*=1.5;
    u = optmonoflow(I1,I2,u,smooth,(float)(precision/std::pow(2.25,1+scale)),disp);
    std::fprintf(stderr,"\n");
  }
  return u;
}


/*------------------------

  Main function

  ------------------------*/

int main(int argc,char **argv) {
  
  // Read command line parameters
  cimg_usage("Compute an optical flow between two 2D images, and create a warped animation");
  const char
    *name_i1   = cimg_option("-i","img/sh0r.pgm","Input Image 1 (Destination)"),
    *name_i2   = cimg_option("-i2","img/sh1r.pgm","Input Image 2 (Source)"),
    *name_o    = cimg_option("-o",(const char*)NULL,"Output 2D flow (inrimage)"),
    *name_seq  = cimg_option("-o2",(const char*)NULL,"Output Warping Sequence");
  const float
    smooth    = (float)cimg_option("-s",0.1f,"Flow Smoothness"),
    precision = (float)cimg_option("-p",0.9f,"Convergence precision");
  const unsigned int
    nb        = cimg_option("-n",40,"Number of warped frames"),
    nbscale   = cimg_option("-scale",0,"Number of scales (0=auto)");
  const bool
    normalize = cimg_option("-equalize",true,"Histogram normalization of the images"),
    morph     = cimg_option("-m",true,"Morphing mode"),
    imode     = cimg_option("-c",true,"Complete interpolation (or last frame is missing)"),
    dispflag = !cimg_option("-novisu",false,"Visualization");
  
  // Init images and display
  std::fprintf(stderr," - Init images.\n");
  const CImg<>
    src(name_i1),
    dest(CImg<>(name_i2).resize(src,3)),
    src_blur  = normalize?src.get_blur(0.5f).equalize_histogram():src.get_blur(0.5f),
    dest_blur = normalize?dest.get_blur(0.5f).equalize_histogram():dest.get_blur(0.5f);
  
  CImgDisplay *disp = NULL;
  if (dispflag) {
    unsigned int w = src.width, h = src.height;
    const unsigned int dmin = cimg::min(w,h), minsiz = 512;
    if (dmin<minsiz) { w=w*minsiz/dmin; h=h*minsiz/dmin; }
    const unsigned int dmax = cimg::max(w,h), maxsiz = 1024;
    if (dmax>maxsiz) { w=w*maxsiz/dmax; h=h*maxsiz/dmax; }
    disp = new CImgDisplay(w,h,"Estimated Motion",0,3);
  }

  // Run Motion estimation algorithm
  std::fprintf(stderr," - Compute optical flow.\n");
  const CImg<> u = optflow(src_blur,dest_blur,smooth,precision,nbscale,disp);
  if (name_o) u.save(name_o);
  u.print("Computed flow");
  
  // Do morphing animation
  std::fprintf(stderr," - Create warped animation.\n");
  CImgDisplay *disp2 = NULL;
  if (dispflag) {
    unsigned int w = src.width, h = src.height;
    const unsigned int dmin = cimg::min(w,h), minsiz = 100;
    if (dmin<minsiz) { w=w*minsiz/dmin; h=h*minsiz/dmin; }
    const unsigned int dmax = cimg::max(w,h), maxsiz = 1024/3;
    if (dmax>maxsiz) { w=w*maxsiz/dmax; h=h*maxsiz/dmax; }
    disp2 = new CImgDisplay(3*w,h,"Source/Destination images and Motion animation",0,19);
  }
  animate_warp(src.get_normalize(0,255),dest.get_normalize(0,255),u,morph,imode,name_seq,nb,disp2);
  
  if (disp) delete disp;
  if (disp2) delete disp2;
  exit(0);
  return 0;
}
