vpImageTools.h

/****************************************************************************
 *
 * This file is part of the ViSP software.
 * Copyright (C) 2005 - 2017 by Inria. All rights reserved.
 *
 * This software is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * See the file LICENSE.txt at the root directory of this source
 * distribution for additional information about the GNU GPL.
 *
 * For using ViSP with software that can not be combined with the GNU
 * GPL, please contact Inria about acquiring a ViSP Professional
 * Edition License.
 *
 * See http://visp.inria.fr for more information.
 *
 * This software was developed at:
 * Inria Rennes - Bretagne Atlantique
 * Campus Universitaire de Beaulieu
 * 35042 Rennes Cedex
 * France
 *
 * If you have questions regarding the use of this file, please contact
 * Inria at visp@inria.fr
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Description:
 * Image tools.
 *
 * Authors:
 * Fabien Spindler
 *
 *****************************************************************************/

#ifndef vpImageTools_H
#define vpImageTools_H

#include <visp3/core/vpImage.h>

#ifdef VISP_HAVE_PTHREAD
#include <pthread.h>
#endif

#include <visp3/core/vpCameraParameters.h>
#include <visp3/core/vpImageException.h>
#include <visp3/core/vpMath.h>
#include <visp3/core/vpRect.h>

#include <fstream>
#include <iostream>
#include <math.h>
#include <string.h>

class VISP_EXPORT vpImageTools
{
public:
  enum vpImageInterpolationType {
    INTERPOLATION_NEAREST, 
    INTERPOLATION_LINEAR,  
    INTERPOLATION_CUBIC    
  };

  template <class Type>
  static inline void binarise(vpImage<Type> &I, Type threshold1, Type threshold2, Type value1, Type value2, Type value3,
                              const bool useLUT = true);
  static void changeLUT(vpImage<unsigned char> &I, unsigned char A, unsigned char newA, unsigned char B,
                        unsigned char newB);

  template <class Type>
  static void crop(const vpImage<Type> &I, double roi_top, double roi_left, unsigned int roi_height,
                   unsigned int roi_width, vpImage<Type> &crop, unsigned int v_scale = 1, unsigned int h_scale = 1);

  template <class Type>
  static void crop(const vpImage<Type> &I, const vpImagePoint &topLeft, unsigned int roi_height, unsigned int roi_width,
                   vpImage<Type> &crop, unsigned int v_scale = 1, unsigned int h_scale = 1);
  template <class Type>
  static void crop(const vpImage<Type> &I, const vpRect &roi, vpImage<Type> &crop, unsigned int v_scale = 1,
                   unsigned int h_scale = 1);
  template <class Type>
  static void crop(const unsigned char *bitmap, unsigned int width, unsigned int height, const vpRect &roi,
                   vpImage<Type> &crop, unsigned int v_scale = 1, unsigned int h_scale = 1);

  template <class Type> static void flip(const vpImage<Type> &I, vpImage<Type> &newI);

  template <class Type> static void flip(vpImage<Type> &I);

  static void imageDifference(const vpImage<unsigned char> &I1, const vpImage<unsigned char> &I2,
                              vpImage<unsigned char> &Idiff);
  static void imageDifference(const vpImage<vpRGBa> &I1, const vpImage<vpRGBa> &I2, vpImage<vpRGBa> &Idiff);

  static void imageDifferenceAbsolute(const vpImage<unsigned char> &I1, const vpImage<unsigned char> &I2,
                                      vpImage<unsigned char> &Idiff);
  static void imageDifferenceAbsolute(const vpImage<vpRGBa> &I1, const vpImage<vpRGBa> &I2, vpImage<vpRGBa> &Idiff);

  static void imageAdd(const vpImage<unsigned char> &I1, const vpImage<unsigned char> &I2, vpImage<unsigned char> &Ires,
                       const bool saturate = false);

  static void imageSubtract(const vpImage<unsigned char> &I1, const vpImage<unsigned char> &I2,
                            vpImage<unsigned char> &Ires, const bool saturate = false);

  template <class Type>
  static void resize(const vpImage<Type> &I, vpImage<Type> &Ires, const unsigned int width, const unsigned int height,
                     const vpImageInterpolationType &method = INTERPOLATION_NEAREST);

  template <class Type>
  static void resize(const vpImage<Type> &I, vpImage<Type> &Ires,
                     const vpImageInterpolationType &method = INTERPOLATION_NEAREST);

  template <class Type>
  static void undistort(const vpImage<Type> &I, const vpCameraParameters &cam, vpImage<Type> &newI);

#if defined(VISP_BUILD_DEPRECATED_FUNCTIONS)

  template <class Type>
  vp_deprecated static void createSubImage(const vpImage<Type> &I, unsigned int i_sub, unsigned int j_sub,
                                           unsigned int nrow_sub, unsigned int ncol_sub, vpImage<Type> &S);

  template <class Type>
  vp_deprecated static void createSubImage(const vpImage<Type> &I, const vpRect &rect, vpImage<Type> &S);
#endif

private:
  // Cubic interpolation
  static float cubicHermite(const float A, const float B, const float C, const float D, const float t);

  template <class Type> static Type getPixelClamped(const vpImage<Type> &I, const float u, const float v);

  // Linear interpolation
  static float lerp(const float A, const float B, const float t);

  template <class Type>
  static void resizeBicubic(const vpImage<Type> &I, vpImage<Type> &Ires, const unsigned int i, const unsigned int j,
                            const float u, const float v, const float xFrac, const float yFrac);

  template <class Type>
  static void resizeBilinear(const vpImage<Type> &I, vpImage<Type> &Ires, const unsigned int i, const unsigned int j,
                             const float u, const float v, const float xFrac, const float yFrac);

  template <class Type>
  static void resizeNearest(const vpImage<Type> &I, vpImage<Type> &Ires, const unsigned int i, const unsigned int j,
                            const float u, const float v);
};

#if defined(VISP_BUILD_DEPRECATED_FUNCTIONS)

template <class Type>
void vpImageTools::createSubImage(const vpImage<Type> &I, unsigned int roi_top, unsigned int roi_left,
                                  unsigned int roi_height, unsigned int roi_width, vpImage<Type> &crop)
{
  vpImageTools::crop(I, roi_top, roi_left, roi_height, roi_width, crop);
}

template <class Type> void vpImageTools::createSubImage(const vpImage<Type> &I, const vpRect &roi, vpImage<Type> &crop)
{
  vpImageTools::crop(I, roi, crop);
}

#endif // #if defined(VISP_BUILD_DEPRECATED_FUNCTIONS)

template <class Type>
void vpImageTools::crop(const vpImage<Type> &I, double roi_top, double roi_left, unsigned int roi_height,
                        unsigned int roi_width, vpImage<Type> &crop, unsigned int v_scale, unsigned int h_scale)
{
  int i_min = (std::max)((int)(ceil(roi_top / v_scale)), 0);
  int j_min = (std::max)((int)(ceil(roi_left / h_scale)), 0);
  int i_max = (std::min)((int)(ceil((roi_top + roi_height)) / v_scale), (int)(I.getHeight() / v_scale));
  int j_max = (std::min)((int)(ceil((roi_left + roi_width) / h_scale)), (int)(I.getWidth() / h_scale));

  unsigned int i_min_u = (unsigned int)i_min;
  unsigned int j_min_u = (unsigned int)j_min;

  unsigned int r_width = (unsigned int)(j_max - j_min);
  unsigned int r_height = (unsigned int)(i_max - i_min);

  crop.resize(r_height, r_width);

  if (v_scale == 1 && h_scale == 1) {
    for (unsigned int i = 0; i < r_height; i++) {
      void *src = (void *)(I[i + i_min_u] + j_min_u);
      void *dst = (void *)crop[i];
      memcpy(dst, src, r_width * sizeof(Type));
    }
  } else if (h_scale == 1) {
    for (unsigned int i = 0; i < r_height; i++) {
      void *src = (void *)(I[(i + i_min_u) * v_scale] + j_min_u);
      void *dst = (void *)crop[i];
      memcpy(dst, src, r_width * sizeof(Type));
    }
  } else {
    for (unsigned int i = 0; i < r_height; i++) {
      for (unsigned int j = 0; j < r_width; j++) {
        crop[i][j] = I[(i + i_min_u) * v_scale][(j + j_min_u) * h_scale];
      }
    }
  }
}

template <class Type>
void vpImageTools::crop(const vpImage<Type> &I, const vpImagePoint &topLeft, unsigned int roi_height,
                        unsigned int roi_width, vpImage<Type> &crop, unsigned int v_scale, unsigned int h_scale)
{
  vpImageTools::crop(I, topLeft.get_i(), topLeft.get_j(), roi_height, roi_width, crop, v_scale, h_scale);
}

template <class Type>
void vpImageTools::crop(const vpImage<Type> &I, const vpRect &roi, vpImage<Type> &crop, unsigned int v_scale,
                        unsigned int h_scale)
{
  vpImageTools::crop(I, roi.getTop(), roi.getLeft(), (unsigned int)roi.getHeight(), (unsigned int)roi.getWidth(), crop,
                     v_scale, h_scale);
}

template <class Type>
void vpImageTools::crop(const unsigned char *bitmap, unsigned int width, unsigned int height, const vpRect &roi,
                        vpImage<Type> &crop, unsigned int v_scale, unsigned int h_scale)
{
  int i_min = (std::max)((int)(ceil(roi.getTop() / v_scale)), 0);
  int j_min = (std::max)((int)(ceil(roi.getLeft() / h_scale)), 0);
  int i_max = (std::min)((int)(ceil((roi.getTop() + roi.getHeight())) / v_scale), (int)(height / v_scale));
  int j_max = (std::min)((int)(ceil((roi.getLeft() + roi.getWidth()) / h_scale)), (int)(width / h_scale));

  unsigned int i_min_u = (unsigned int)i_min;
  unsigned int j_min_u = (unsigned int)j_min;

  unsigned int r_width = (unsigned int)(j_max - j_min);
  unsigned int r_height = (unsigned int)(i_max - i_min);

  crop.resize(r_height, r_width);

  if (v_scale == 1 && h_scale == 1) {
    for (unsigned int i = 0; i < r_height; i++) {
      void *src = (void *)(bitmap + ((i + i_min_u) * width + j_min_u) * sizeof(Type));
      void *dst = (void *)crop[i];
      memcpy(dst, src, r_width * sizeof(Type));
    }
  } else if (h_scale == 1) {
    for (unsigned int i = 0; i < r_height; i++) {
      void *src = (void *)(bitmap + ((i + i_min_u) * width * v_scale + j_min_u) * sizeof(Type));
      void *dst = (void *)crop[i];
      memcpy(dst, src, r_width * sizeof(Type));
    }
  } else {
    for (unsigned int i = 0; i < r_height; i++) {
      unsigned int i_src = (i + i_min_u) * width * v_scale + j_min_u * h_scale;
      for (unsigned int j = 0; j < r_width; j++) {
        void *src = (void *)(bitmap + (i_src + j * h_scale) * sizeof(Type));
        void *dst = (void *)&crop[i][j];
        memcpy(dst, src, sizeof(Type));
      }
    }
  }
}

template <class Type>
inline void vpImageTools::binarise(vpImage<Type> &I, Type threshold1, Type threshold2, Type value1, Type value2,
                                   Type value3, const bool useLUT)
{
  if (useLUT) {
    std::cerr << "LUT not available for this type ! Will use the iteration method." << std::endl;
  }

  Type v;
  Type *p = I.bitmap;
  Type *pend = I.bitmap + I.getWidth() * I.getHeight();
  for (; p < pend; p++) {
    v = *p;
    if (v < threshold1)
      *p = value1;
    else if (v > threshold2)
      *p = value3;
    else
      *p = value2;
  }
}

template <>
inline void vpImageTools::binarise(vpImage<unsigned char> &I, unsigned char threshold1, unsigned char threshold2,
                                   unsigned char value1, unsigned char value2, unsigned char value3, const bool useLUT)
{
  if (useLUT) {
    // Construct the LUT
    unsigned char lut[256];
    for (unsigned int i = 0; i < 256; i++) {
      lut[i] = i < threshold1 ? value1 : (i > threshold2 ? value3 : value2);
    }

    I.performLut(lut);
  } else {
    unsigned char *p = I.bitmap;
    unsigned char *pend = I.bitmap + I.getWidth() * I.getHeight();
    for (; p < pend; p++) {
      unsigned char v = *p;
      if (v < threshold1)
        *p = value1;
      else if (v > threshold2)
        *p = value3;
      else
        *p = value2;
    }
  }
}

#ifdef VISP_HAVE_PTHREAD

#ifndef DOXYGEN_SHOULD_SKIP_THIS
template <class Type> class vpUndistortInternalType
{
public:
  Type *src;
  Type *dst;
  unsigned int width;
  unsigned int height;
  vpCameraParameters cam;
  unsigned int nthreads;
  unsigned int threadid;

public:
  vpUndistortInternalType() : src(NULL), dst(NULL), width(0), height(0), cam(), nthreads(0), threadid(0){};

  vpUndistortInternalType(const vpUndistortInternalType<Type> &u) { *this = u; };
  vpUndistortInternalType &operator=(const vpUndistortInternalType<Type> &u)
  {
    src = u.src;
    dst = u.dst;
    width = u.width;
    height = u.height;
    cam = u.cam;
    nthreads = u.nthreads;
    threadid = u.threadid;

    return *this;
  }

  static void *vpUndistort_threaded(void *arg);
};

template <class Type> void *vpUndistortInternalType<Type>::vpUndistort_threaded(void *arg)
{
  vpUndistortInternalType<Type> *undistortSharedData = static_cast<vpUndistortInternalType<Type> *>(arg);
  int offset = (int)undistortSharedData->threadid;
  int width = (int)undistortSharedData->width;
  int height = (int)undistortSharedData->height;
  int nthreads = (int)undistortSharedData->nthreads;

  double u0 = undistortSharedData->cam.get_u0();
  double v0 = undistortSharedData->cam.get_v0();
  double px = undistortSharedData->cam.get_px();
  double py = undistortSharedData->cam.get_py();
  double kud = undistortSharedData->cam.get_kud();

  double invpx = 1.0 / px;
  double invpy = 1.0 / py;

  double kud_px2 = kud * invpx * invpx;
  double kud_py2 = kud * invpy * invpy;

  Type *dst = undistortSharedData->dst + (height / nthreads * offset) * width;
  Type *src = undistortSharedData->src;

  for (double v = height / nthreads * offset; v < height / nthreads * (offset + 1); v++) {
    double deltav = v - v0;
    // double fr1 = 1.0 + kd * (vpMath::sqr(deltav * invpy));
    double fr1 = 1.0 + kud_py2 * deltav * deltav;

    for (double u = 0; u < width; u++) {
      // computation of u,v : corresponding pixel coordinates in I.
      double deltau = u - u0;
      // double fr2 = fr1 + kd * (vpMath::sqr(deltau * invpx));
      double fr2 = fr1 + kud_px2 * deltau * deltau;

      double u_double = deltau * fr2 + u0;
      double v_double = deltav * fr2 + v0;

      // computation of the bilinear interpolation

      // declarations
      int u_round = (int)(u_double);
      int v_round = (int)(v_double);
      if (u_round < 0.f)
        u_round = -1;
      if (v_round < 0.f)
        v_round = -1;
      double du_double = (u_double) - (double)u_round;
      double dv_double = (v_double) - (double)v_round;
      Type v01;
      Type v23;
      if ((0 <= u_round) && (0 <= v_round) && (u_round < ((width)-1)) && (v_round < ((height)-1))) {
        // process interpolation
        const Type *_mp = &src[v_round * width + u_round];
        v01 = (Type)(_mp[0] + ((_mp[1] - _mp[0]) * du_double));
        _mp += width;
        v23 = (Type)(_mp[0] + ((_mp[1] - _mp[0]) * du_double));
        *dst = (Type)(v01 + ((v23 - v01) * dv_double));
      } else {
        *dst = 0;
      }
      dst++;
    }
  }

  pthread_exit((void *)0);
  return NULL;
}
#endif // DOXYGEN_SHOULD_SKIP_THIS
#endif // VISP_HAVE_PTHREAD

template <class Type>
void vpImageTools::undistort(const vpImage<Type> &I, const vpCameraParameters &cam, vpImage<Type> &undistI)
{
#ifdef VISP_HAVE_PTHREAD
  //
  // Optimized version using pthreads
  //
  unsigned int width = I.getWidth();
  unsigned int height = I.getHeight();

  undistI.resize(height, width);

  double kud = cam.get_kud();

  // if (kud == 0) {
  if (std::fabs(kud) <= std::numeric_limits<double>::epsilon()) {
    // There is no need to undistort the image
    undistI = I;
    return;
  }

  unsigned int nthreads = 2;
  pthread_attr_t attr;
  pthread_t *callThd = new pthread_t[nthreads];
  pthread_attr_init(&attr);
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

  vpUndistortInternalType<Type> *undistortSharedData;
  undistortSharedData = new vpUndistortInternalType<Type>[nthreads];

  for (unsigned int i = 0; i < nthreads; i++) {
    // Each thread works on a different set of data.
    //    vpTRACE("create thread %d", i);
    undistortSharedData[i].src = I.bitmap;
    undistortSharedData[i].dst = undistI.bitmap;
    undistortSharedData[i].width = I.getWidth();
    undistortSharedData[i].height = I.getHeight();
    undistortSharedData[i].cam = cam;
    undistortSharedData[i].nthreads = nthreads;
    undistortSharedData[i].threadid = i;
    pthread_create(&callThd[i], &attr, &vpUndistortInternalType<Type>::vpUndistort_threaded, &undistortSharedData[i]);
  }
  pthread_attr_destroy(&attr);
  /* Wait on the other threads */

  for (unsigned int i = 0; i < nthreads; i++) {
    //  vpTRACE("join thread %d", i);
    pthread_join(callThd[i], NULL);
  }

  delete[] callThd;
  delete[] undistortSharedData;
#else  // VISP_HAVE_PTHREAD
  //
  // optimized version without pthreads
  //
  unsigned int width = I.getWidth();
  unsigned int height = I.getHeight();

  undistI.resize(height, width);

  double u0 = cam.get_u0();
  double v0 = cam.get_v0();
  double px = cam.get_px();
  double py = cam.get_py();
  double kud = cam.get_kud();

  // if (kud == 0) {
  if (std::fabs(kud) <= std::numeric_limits<double>::epsilon()) {
    // There is no need to undistort the image
    undistI = I;
    return;
  }

  double invpx = 1.0 / px;
  double invpy = 1.0 / py;

  double kud_px2 = kud * invpx * invpx;
  double kud_py2 = kud * invpy * invpy;

  Type *dst = undistI.bitmap;
  for (double v = 0; v < height; v++) {
    double deltav = v - v0;
    // double fr1 = 1.0 + kd * (vpMath::sqr(deltav * invpy));
    double fr1 = 1.0 + kud_py2 * deltav * deltav;

    for (double u = 0; u < width; u++) {
      // computation of u,v : corresponding pixel coordinates in I.
      double deltau = u - u0;
      // double fr2 = fr1 + kd * (vpMath::sqr(deltau * invpx));
      double fr2 = fr1 + kud_px2 * deltau * deltau;

      double u_double = deltau * fr2 + u0;
      double v_double = deltav * fr2 + v0;

      // printf("[%g][%g] %g %g : ", u, v, u_double, v_double );

      // computation of the bilinear interpolation

      // declarations
      int u_round = (int)(u_double);
      int v_round = (int)(v_double);
      if (u_round < 0.f)
        u_round = -1;
      if (v_round < 0.f)
        v_round = -1;
      double du_double = (u_double) - (double)u_round;
      double dv_double = (v_double) - (double)v_round;
      Type v01;
      Type v23;
      if ((0 <= u_round) && (0 <= v_round) && (u_round < (((int)width) - 1)) && (v_round < (((int)height) - 1))) {
        // process interpolation
        const Type *_mp = &I[(unsigned int)v_round][(unsigned int)u_round];
        v01 = (Type)(_mp[0] + ((_mp[1] - _mp[0]) * du_double));
        _mp += width;
        v23 = (Type)(_mp[0] + ((_mp[1] - _mp[0]) * du_double));
        *dst = (Type)(v01 + ((v23 - v01) * dv_double));
        // printf("R %d G %d B %d\n", dst->R, dst->G, dst->B);
      } else {
        *dst = 0;
      }
      dst++;
    }
  }
#endif // VISP_HAVE_PTHREAD

#if 0
  // non optimized version
  int width = I.getWidth();
  int height = I.getHeight();

  undistI.resize(height,width);

  double u0 = cam.get_u0();
  double v0 = cam.get_v0();
  double px = cam.get_px();
  double py = cam.get_py();
  double kd = cam.get_kud();

  if (kd == 0) {
    // There is no need to undistort the image
    undistI = I;
    return;
  }

  for(int v = 0 ; v < height; v++){
    for(int u = 0; u < height; u++){
      double r2 = vpMath::sqr(((double)u - u0)/px) +
                  vpMath::sqr(((double)v-v0)/py);
      double u_double = ((double)u - u0)*(1.0+kd*r2) + u0;
      double v_double = ((double)v - v0)*(1.0+kd*r2) + v0;
      undistI[v][u] = I.getPixelBI((float)u_double,(float)v_double);
    }
  }
#endif
}

template <class Type> void vpImageTools::flip(const vpImage<Type> &I, vpImage<Type> &newI)
{
  unsigned int height = 0, width = 0;

  height = I.getHeight();
  width = I.getWidth();
  newI.resize(height, width);

  for (unsigned int i = 0; i < height; i++) {
    memcpy(newI.bitmap + i * width, I.bitmap + (height - 1 - i) * width, width * sizeof(Type));
  }
}

template <class Type> void vpImageTools::flip(vpImage<Type> &I)
{
  unsigned int height = 0, width = 0;
  unsigned int i = 0;
  vpImage<Type> Ibuf;

  height = I.getHeight();
  width = I.getWidth();
  Ibuf.resize(1, width);

  for (i = 0; i < height / 2; i++) {
    memcpy(Ibuf.bitmap, I.bitmap + i * width, width * sizeof(Type));

    memcpy(I.bitmap + i * width, I.bitmap + (height - 1 - i) * width, width * sizeof(Type));
    memcpy(I.bitmap + (height - 1 - i) * width, Ibuf.bitmap, width * sizeof(Type));
  }
}

template <class Type> Type vpImageTools::getPixelClamped(const vpImage<Type> &I, const float u, const float v)
{
  unsigned int i, j;
  if (u < 0.)
    j = 0;
  else if (u > (float)I.getWidth() - 1.)
    j = I.getWidth() - 1;
  else
    j = (unsigned int)u;

  if (v < 0.)
    i = 0;
  else if (v > (float)I.getHeight() - 1.)
    i = I.getHeight() - 1;
  else
    i = (unsigned int)v;

  return I[i][j];
}

// Reference:
// http://blog.demofox.org/2015/08/15/resizing-images-with-bicubic-interpolation/
template <class Type>
void vpImageTools::resizeBicubic(const vpImage<Type> &I, vpImage<Type> &Ires, const unsigned int i,
                                 const unsigned int j, const float u, const float v, const float xFrac,
                                 const float yFrac)
{
  // 1st row
  Type p00 = getPixelClamped(I, u - 1, v - 1);
  Type p01 = getPixelClamped(I, u + 0, v - 1);
  Type p02 = getPixelClamped(I, u + 1, v - 1);
  Type p03 = getPixelClamped(I, u + 2, v - 1);

  // 2nd row
  Type p10 = getPixelClamped(I, u - 1, v + 0);
  Type p11 = getPixelClamped(I, u + 0, v + 0);
  Type p12 = getPixelClamped(I, u + 1, v + 0);
  Type p13 = getPixelClamped(I, u + 2, v + 0);

  // 3rd row
  Type p20 = getPixelClamped(I, u - 1, v + 1);
  Type p21 = getPixelClamped(I, u + 0, v + 1);
  Type p22 = getPixelClamped(I, u + 1, v + 1);
  Type p23 = getPixelClamped(I, u + 2, v + 1);

  // 4th row
  Type p30 = getPixelClamped(I, u - 1, v + 2);
  Type p31 = getPixelClamped(I, u + 0, v + 2);
  Type p32 = getPixelClamped(I, u + 1, v + 2);
  Type p33 = getPixelClamped(I, u + 2, v + 2);

  float col0 = cubicHermite(p00, p01, p02, p03, xFrac);
  float col1 = cubicHermite(p10, p11, p12, p13, xFrac);
  float col2 = cubicHermite(p20, p21, p22, p23, xFrac);
  float col3 = cubicHermite(p30, p31, p32, p33, xFrac);
  float value = cubicHermite(col0, col1, col2, col3, yFrac);
  Ires[i][j] = vpMath::saturate<Type>(value);
}

template <>
inline void vpImageTools::resizeBicubic(const vpImage<vpRGBa> &I, vpImage<vpRGBa> &Ires, const unsigned int i,
                                        const unsigned int j, const float u, const float v, const float xFrac,
                                        const float yFrac)
{
  // 1st row
  vpRGBa p00 = getPixelClamped(I, u - 1, v - 1);
  vpRGBa p01 = getPixelClamped(I, u + 0, v - 1);
  vpRGBa p02 = getPixelClamped(I, u + 1, v - 1);
  vpRGBa p03 = getPixelClamped(I, u + 2, v - 1);

  // 2nd row
  vpRGBa p10 = getPixelClamped(I, u - 1, v + 0);
  vpRGBa p11 = getPixelClamped(I, u + 0, v + 0);
  vpRGBa p12 = getPixelClamped(I, u + 1, v + 0);
  vpRGBa p13 = getPixelClamped(I, u + 2, v + 0);

  // 3rd row
  vpRGBa p20 = getPixelClamped(I, u - 1, v + 1);
  vpRGBa p21 = getPixelClamped(I, u + 0, v + 1);
  vpRGBa p22 = getPixelClamped(I, u + 1, v + 1);
  vpRGBa p23 = getPixelClamped(I, u + 2, v + 1);

  // 4th row
  vpRGBa p30 = getPixelClamped(I, u - 1, v + 2);
  vpRGBa p31 = getPixelClamped(I, u + 0, v + 2);
  vpRGBa p32 = getPixelClamped(I, u + 1, v + 2);
  vpRGBa p33 = getPixelClamped(I, u + 2, v + 2);

  for (int c = 0; c < 3; c++) {
    float col0 = cubicHermite(((unsigned char *)&p00)[c], ((unsigned char *)&p01)[c], ((unsigned char *)&p02)[c],
                              ((unsigned char *)&p03)[c], xFrac);
    float col1 = cubicHermite(((unsigned char *)&p10)[c], ((unsigned char *)&p11)[c], ((unsigned char *)&p12)[c],
                              ((unsigned char *)&p13)[c], xFrac);
    float col2 = cubicHermite(((unsigned char *)&p20)[c], ((unsigned char *)&p21)[c], ((unsigned char *)&p22)[c],
                              ((unsigned char *)&p23)[c], xFrac);
    float col3 = cubicHermite(((unsigned char *)&p30)[c], ((unsigned char *)&p31)[c], ((unsigned char *)&p32)[c],
                              ((unsigned char *)&p33)[c], xFrac);
    float value = cubicHermite(col0, col1, col2, col3, yFrac);

    ((unsigned char *)&Ires[i][j])[c] = vpMath::saturate<unsigned char>(value);
  }
}

template <class Type>
void vpImageTools::resizeBilinear(const vpImage<Type> &I, vpImage<Type> &Ires, const unsigned int i,
                                  const unsigned int j, const float u, const float v, const float xFrac,
                                  const float yFrac)
{
  unsigned int u0 = (unsigned int)u;
  unsigned int v0 = (unsigned int)v;

  unsigned int u1 = (std::min)(I.getWidth() - 1, (unsigned int)u + 1);
  unsigned int v1 = v0;

  unsigned int u2 = u0;
  unsigned int v2 = (std::min)(I.getHeight() - 1, (unsigned int)v + 1);

  unsigned int u3 = (std::min)(I.getWidth() - 1, (unsigned int)u + 1);
  unsigned int v3 = (std::min)(I.getHeight() - 1, (unsigned int)v + 1);

  float col0 = lerp(I[v0][u0], I[v1][u1], xFrac);
  float col1 = lerp(I[v2][u2], I[v3][u3], xFrac);
  float value = lerp(col0, col1, yFrac);

  Ires[i][j] = vpMath::saturate<Type>(value);
}

template <>
inline void vpImageTools::resizeBilinear(const vpImage<vpRGBa> &I, vpImage<vpRGBa> &Ires, const unsigned int i,
                                         const unsigned int j, const float u, const float v, const float xFrac,
                                         const float yFrac)
{
  unsigned int u0 = (unsigned int)u;
  unsigned int v0 = (unsigned int)v;

  unsigned int u1 = (std::min)(I.getWidth() - 1, (unsigned int)u + 1);
  unsigned int v1 = v0;

  unsigned int u2 = u0;
  unsigned int v2 = (std::min)(I.getHeight() - 1, (unsigned int)v + 1);

  unsigned int u3 = (std::min)(I.getWidth() - 1, (unsigned int)u + 1);
  unsigned int v3 = (std::min)(I.getHeight() - 1, (unsigned int)v + 1);

  for (int c = 0; c < 3; c++) {
    float col0 = lerp(((unsigned char *)&I[v0][u0])[c], ((unsigned char *)&I[v1][u1])[c], xFrac);
    float col1 = lerp(((unsigned char *)&I[v2][u2])[c], ((unsigned char *)&I[v3][u3])[c], xFrac);
    float value = lerp(col0, col1, yFrac);

    ((unsigned char *)&Ires[i][j])[c] = vpMath::saturate<unsigned char>(value);
  }
}

template <class Type>
void vpImageTools::resizeNearest(const vpImage<Type> &I, vpImage<Type> &Ires, const unsigned int i,
                                 const unsigned int j, const float u, const float v)
{
  Ires[i][j] = getPixelClamped(I, u, v);
}

template <class Type>
void vpImageTools::resize(const vpImage<Type> &I, vpImage<Type> &Ires, const unsigned int width,
                          const unsigned int height, const vpImageInterpolationType &method)
{
  Ires.resize(height, width);

  vpImageTools::resize(I, Ires, method);
}

template <class Type>
void vpImageTools::resize(const vpImage<Type> &I, vpImage<Type> &Ires, const vpImageInterpolationType &method)
{
  if (I.getWidth() < 2 || I.getHeight() < 2 || Ires.getWidth() < 2 || Ires.getHeight() < 2) {
    std::cerr << "Input or output image is too small!" << std::endl;
    return;
  }

  float scaleY = (I.getHeight() - 1) / (float)(Ires.getHeight() - 1);
  float scaleX = (I.getWidth() - 1) / (float)(Ires.getWidth() - 1);

  if (method == INTERPOLATION_NEAREST) {
    scaleY = I.getHeight() / (float)(Ires.getHeight() - 1);
    scaleX = I.getWidth() / (float)(Ires.getWidth() - 1);
  }

  for (unsigned int i = 0; i < Ires.getHeight(); i++) {
    float v = i * scaleY;
    float yFrac = v - (int)v;

    for (unsigned int j = 0; j < Ires.getWidth(); j++) {
      float u = j * scaleX;
      float xFrac = u - (int)u;

      if (method == INTERPOLATION_NEAREST) {
        resizeNearest(I, Ires, i, j, u, v);
      } else if (method == INTERPOLATION_LINEAR) {
        resizeBilinear(I, Ires, i, j, u, v, xFrac, yFrac);
      } else if (method == INTERPOLATION_CUBIC) {
        resizeBicubic(I, Ires, i, j, u, v, xFrac, yFrac);
      }
    }
  }
}

#endif