vpImageIo.cpp

/****************************************************************************
 *
 * ViSP, open source Visual Servoing Platform software.
 * Copyright (C) 2005 - 2019 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:
 * Read/write images.
 *
 * Authors:
 * Eric Marchand
 *
 *****************************************************************************/

#include <visp3/core/vpImage.h>
#include <visp3/core/vpImageConvert.h> //image  conversion
#include <visp3/core/vpIoTools.h>
#include <visp3/io/vpImageIo.h>

#if defined(_WIN32)
// Include WinSock2.h before windows.h to ensure that winsock.h is not
// included by windows.h since winsock.h and winsock2.h are incompatible
#include <WinSock2.h>
#include <windows.h>
#endif

#if defined(VISP_HAVE_JPEG)
#include <jerror.h>
#include <jpeglib.h>
#endif

#if defined(VISP_HAVE_PNG)
#include <png.h>
#endif

#if !defined(VISP_HAVE_OPENCV)
#if !defined(VISP_HAVE_JPEG) || !defined(VISP_HAVE_PNG)

#if defined __SSE2__ || defined _M_X64 || (defined _M_IX86_FP && _M_IX86_FP >= 2)
#  define VISP_HAVE_SSE2 1
#endif

#ifndef VISP_HAVE_SSE2
#  define STBI_NO_SIMD
#endif

#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>

#define STB_IMAGE_WRITE_IMPLEMENTATION
#include <stb_image_write.h>
#endif
#endif

void vp_decodeHeaderPNM(const std::string &filename, std::ifstream &fd, const std::string &magic, unsigned int &w,
                        unsigned int &h, unsigned int &maxval);

#ifndef DOXYGEN_SHOULD_SKIP_THIS

void vp_decodeHeaderPNM(const std::string &filename, std::ifstream &fd, const std::string &magic, unsigned int &w,
                        unsigned int &h, unsigned int &maxval)
{
  std::string line;
  unsigned int nb_elt = 4, cpt_elt = 0;
  while (cpt_elt != nb_elt) {
    // Skip empty lines or lines starting with # (comment)
    while (std::getline(fd, line) && (line.compare(0, 1, "#") == 0 || line.size() == 0)) {
    };

    if (fd.eof()) {
      fd.close();
      throw(vpImageException(vpImageException::ioError, "Cannot read header of file \"%s\"", filename.c_str()));
    }

    std::vector<std::string> header = vpIoTools::splitChain(line, std::string(" "));

    if (header.size() == 0) {
      fd.close();
      throw(vpImageException(vpImageException::ioError, "Cannot read header of file \"%s\"", filename.c_str()));
    }

    if (cpt_elt == 0) { // decode magic
      if (header[0].compare(0, magic.size(), magic) != 0) {
        fd.close();
        throw(vpImageException(vpImageException::ioError, "\"%s\" is not a PNM file with magic number %s",
                               filename.c_str(), magic.c_str()));
      }
      cpt_elt++;
      header.erase(header.begin(),
                   header.begin() + 1); // erase first element that is processed
    }
    while (header.size()) {
      if (cpt_elt == 1) { // decode width
        std::istringstream ss(header[0]);
        ss >> w;
        cpt_elt++;
        header.erase(header.begin(),
                     header.begin() + 1); // erase first element that is processed
      } else if (cpt_elt == 2) {          // decode height
        std::istringstream ss(header[0]);
        ss >> h;
        cpt_elt++;
        header.erase(header.begin(),
                     header.begin() + 1); // erase first element that is processed
      } else if (cpt_elt == 3) {          // decode maxval
        std::istringstream ss(header[0]);
        ss >> maxval;
        cpt_elt++;
        header.erase(header.begin(),
                     header.begin() + 1); // erase first element that is processed
      }
    }
  }
}
#endif

vpImageIo::vpImageFormatType vpImageIo::getFormat(const std::string &filename)
{
  std::string ext = vpImageIo::getExtension(filename);

  if (ext.compare(".PGM") == 0)
    return FORMAT_PGM;
  else if (ext.compare(".pgm") == 0)
    return FORMAT_PGM;
  else if (ext.compare(".PPM") == 0)
    return FORMAT_PPM;
  else if (ext.compare(".ppm") == 0)
    return FORMAT_PPM;
  else if (ext.compare(".JPG") == 0)
    return FORMAT_JPEG;
  else if (ext.compare(".jpg") == 0)
    return FORMAT_JPEG;
  else if (ext.compare(".JPEG") == 0)
    return FORMAT_JPEG;
  else if (ext.compare(".jpeg") == 0)
    return FORMAT_JPEG;
  else if (ext.compare(".PNG") == 0)
    return FORMAT_PNG;
  else if (ext.compare(".png") == 0)
    return FORMAT_PNG;
  // Formats supported by opencv
  else if (ext.compare(".TIFF") == 0)
    return FORMAT_TIFF;
  else if (ext.compare(".tiff") == 0)
    return FORMAT_TIFF;
  else if (ext.compare(".TIF") == 0)
    return FORMAT_TIFF;
  else if (ext.compare(".tif") == 0)
    return FORMAT_TIFF;
  else if (ext.compare(".BMP") == 0)
    return FORMAT_BMP;
  else if (ext.compare(".bmp") == 0)
    return FORMAT_BMP;
  else if (ext.compare(".DIB") == 0)
    return FORMAT_DIB;
  else if (ext.compare(".dib") == 0)
    return FORMAT_DIB;
  else if (ext.compare(".PBM") == 0)
    return FORMAT_PBM;
  else if (ext.compare(".pbm") == 0)
    return FORMAT_PBM;
  else if (ext.compare(".SR") == 0)
    return FORMAT_RASTER;
  else if (ext.compare(".sr") == 0)
    return FORMAT_RASTER;
  else if (ext.compare(".RAS") == 0)
    return FORMAT_RASTER;
  else if (ext.compare(".ras") == 0)
    return FORMAT_RASTER;
  else if (ext.compare(".JP2") == 0)
    return FORMAT_JPEG2000;
  else if (ext.compare(".jp2") == 0)
    return FORMAT_JPEG2000;
  else
    return FORMAT_UNKNOWN;
}

// return the extension of the file including the dot
std::string vpImageIo::getExtension(const std::string &filename)
{
  // extract the extension
  size_t dot = filename.find_last_of(".");
  std::string ext = filename.substr(dot, filename.size() - 1);
  return ext;
}

void vpImageIo::read(vpImage<unsigned char> &I, const std::string &filename)
{
  bool exist = vpIoTools::checkFilename(filename);
  if (!exist) {
    std::string message = "Cannot read file: \"" + std::string(filename) + "\" doesn't exist";
    throw(vpImageException(vpImageException::ioError, message));
  }

  // Allows to use ~ symbol or env variables in path
  std::string final_filename = vpIoTools::path(filename);

  bool try_opencv_reader = false;

  switch (getFormat(final_filename)) {
  case FORMAT_PGM:
    readPGM(I, final_filename);
    break;
  case FORMAT_PPM:
    readPPM(I, final_filename);
    break;
  case FORMAT_JPEG:
#ifdef VISP_HAVE_JPEG
    readJPEG(I, final_filename);
#else
    try_opencv_reader = true;
#endif
    break;
  case FORMAT_PNG:
#if defined(VISP_HAVE_PNG)
    readPNG(I, final_filename);
#else
    try_opencv_reader = true;
#endif
    break;
  case FORMAT_TIFF:
  case FORMAT_BMP:
  case FORMAT_DIB:
  case FORMAT_PBM:
  case FORMAT_RASTER:
  case FORMAT_JPEG2000:
  case FORMAT_UNKNOWN:
    try_opencv_reader = true;
    break;
  }

  if (try_opencv_reader) {
#if defined(VISP_HAVE_OPENCV) && VISP_HAVE_OPENCV_VERSION >= 0x020100
#if VISP_HAVE_OPENCV_VERSION >= 0x030200
    int flags = cv::IMREAD_GRAYSCALE | cv::IMREAD_IGNORE_ORIENTATION;
#elif VISP_HAVE_OPENCV_VERSION >= 0x030000
    int flags = cv::IMREAD_GRAYSCALE;
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
    int flags = CV_LOAD_IMAGE_GRAYSCALE;
#endif
    // std::cout << "Use opencv to read the image" << std::endl;
    cv::Mat cvI = cv::imread(final_filename, flags);
    if (cvI.cols == 0 && cvI.rows == 0) {
      std::string message = "Cannot read file \"" + std::string(final_filename) + "\": Image format not supported";
      throw(vpImageException(vpImageException::ioError, message));
    }
    vpImageConvert::convert(cvI, I);
#else
    switch (getFormat(final_filename)) {
    case FORMAT_JPEG:
      readJPEG(I, final_filename);
      break;
    case FORMAT_PNG:
      readPNG(I, final_filename);
      break;
    case FORMAT_BMP:
    case FORMAT_TIFF:
    case FORMAT_DIB:
    case FORMAT_PBM:
    case FORMAT_RASTER:
    case FORMAT_JPEG2000:
    case FORMAT_UNKNOWN:
    default:
      std::string message = "Cannot read file \"" + std::string(final_filename) + "\": Image format not supported";
      throw(vpImageException(vpImageException::ioError, message));
    }
#endif
  }
}

void vpImageIo::read(vpImage<vpRGBa> &I, const std::string &filename)
{
  bool exist = vpIoTools::checkFilename(filename);
  if (!exist) {
    std::string message = "Cannot read file: \"" + std::string(filename) + "\" doesn't exist";
    throw(vpImageException(vpImageException::ioError, message));
  }
  // Allows to use ~ symbol or env variables in path
  std::string final_filename = vpIoTools::path(filename);

  bool try_opencv_reader = false;

  switch (getFormat(final_filename)) {
  case FORMAT_PGM:
    readPGM(I, final_filename);
    break;
  case FORMAT_PPM:
    readPPM(I, final_filename);
    break;
  case FORMAT_JPEG:
#ifdef VISP_HAVE_JPEG
    readJPEG(I, final_filename);
#else
    try_opencv_reader = true;
#endif
    break;
  case FORMAT_PNG:
#if defined(VISP_HAVE_PNG)
    readPNG(I, final_filename);
#else
    try_opencv_reader = true;
#endif
    break;
  case FORMAT_TIFF:
  case FORMAT_BMP:
  case FORMAT_DIB:
  case FORMAT_PBM:
  case FORMAT_RASTER:
  case FORMAT_JPEG2000:
  case FORMAT_UNKNOWN:
    try_opencv_reader = true;
    break;
  }

  if (try_opencv_reader) {
#if defined(VISP_HAVE_OPENCV) && VISP_HAVE_OPENCV_VERSION >= 0x020100
#if VISP_HAVE_OPENCV_VERSION >= 0x030200
    int flags = cv::IMREAD_COLOR | cv::IMREAD_IGNORE_ORIENTATION;
#elif VISP_HAVE_OPENCV_VERSION >= 0x030000
    int flags = cv::IMREAD_COLOR;
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
    int flags = CV_LOAD_IMAGE_COLOR;
#endif
    // std::cout << "Use opencv to read the image" << std::endl;
    cv::Mat cvI = cv::imread(final_filename, flags);
    if (cvI.cols == 0 && cvI.rows == 0) {
      std::string message = "Cannot read file \"" + std::string(final_filename) + "\": Image format not supported";
      throw(vpImageException(vpImageException::ioError, message));
    }
    vpImageConvert::convert(cvI, I);
#else
    switch (getFormat(final_filename)) {
    case FORMAT_JPEG:
      readJPEG(I, final_filename);
      break;
    case FORMAT_PNG:
      readPNG(I, final_filename);
      break;
    case FORMAT_BMP:
    case FORMAT_TIFF:
    case FORMAT_DIB:
    case FORMAT_PBM:
    case FORMAT_RASTER:
    case FORMAT_JPEG2000:
    case FORMAT_UNKNOWN:
    default:
      std::string message = "Cannot read file \"" + std::string(final_filename) + "\": Image format not supported";
      throw(vpImageException(vpImageException::ioError, message));
    }
#endif
  }
}

void vpImageIo::write(const vpImage<unsigned char> &I, const std::string &filename)
{
  bool try_opencv_writer = false;

  switch (getFormat(filename)) {
  case FORMAT_PGM:
    writePGM(I, filename);
    break;
  case FORMAT_PPM:
    writePPM(I, filename);
    break;
  case FORMAT_JPEG:
#ifdef VISP_HAVE_JPEG
    writeJPEG(I, filename);
#else
    try_opencv_writer = true;
#endif
    break;
  case FORMAT_PNG:
#ifdef VISP_HAVE_PNG
    writePNG(I, filename);
#else
    try_opencv_writer = true;
#endif
    break;
  case FORMAT_TIFF:
  case FORMAT_BMP:
  case FORMAT_DIB:
  case FORMAT_PBM:
  case FORMAT_RASTER:
  case FORMAT_JPEG2000:
  case FORMAT_UNKNOWN:
    try_opencv_writer = true;
    break;
  }

  if (try_opencv_writer) {
#if VISP_HAVE_OPENCV_VERSION >= 0x020100
    // std::cout << "Use opencv to write the image" << std::endl;
    cv::Mat cvI;
    vpImageConvert::convert(I, cvI);
    cv::imwrite(filename, cvI);
#else
    switch (getFormat(filename)) {
    case FORMAT_JPEG:
      writeJPEG(I, filename);
      break;
    case FORMAT_PNG:
      writePNG(I, filename);
      break;
    case FORMAT_BMP:
    case FORMAT_TIFF:
    case FORMAT_DIB:
    case FORMAT_PBM:
    case FORMAT_RASTER:
    case FORMAT_JPEG2000:
    case FORMAT_UNKNOWN:
    default:
      vpCERROR << "Cannot write file: Image format not supported..." << std::endl;
      throw(vpImageException(vpImageException::ioError, "Cannot write file: Image format not supported"));
    }
#endif
  }
}

void vpImageIo::write(const vpImage<vpRGBa> &I, const std::string &filename)
{
  bool try_opencv_writer = false;

  switch (getFormat(filename)) {
  case FORMAT_PGM:
    writePGM(I, filename);
    break;
  case FORMAT_PPM:
    writePPM(I, filename);
    break;
  case FORMAT_JPEG:
#ifdef VISP_HAVE_JPEG
    writeJPEG(I, filename);
#else
    try_opencv_writer = true;
#endif
    break;
  case FORMAT_PNG:
#ifdef VISP_HAVE_PNG
    writePNG(I, filename);
#else
    try_opencv_writer = true;
#endif
    break;
  case FORMAT_TIFF:
  case FORMAT_BMP:
  case FORMAT_DIB:
  case FORMAT_PBM:
  case FORMAT_RASTER:
  case FORMAT_JPEG2000:
  case FORMAT_UNKNOWN:
    try_opencv_writer = true;
    break;
  }

  if (try_opencv_writer) {
#if VISP_HAVE_OPENCV_VERSION >= 0x020100
    // std::cout << "Use opencv to write the image" << std::endl;
    cv::Mat cvI;
    vpImageConvert::convert(I, cvI);
    cv::imwrite(filename, cvI);
#else
    switch (getFormat(filename)) {
    case FORMAT_JPEG:
      writeJPEG(I, filename);
      break;
    case FORMAT_PNG:
      writePNG(I, filename);
      break;
    case FORMAT_BMP:
    case FORMAT_TIFF:
    case FORMAT_DIB:
    case FORMAT_PBM:
    case FORMAT_RASTER:
    case FORMAT_JPEG2000:
    case FORMAT_UNKNOWN:
    default:
      vpCERROR << "Cannot write file: Image format not supported..." << std::endl;
      throw(vpImageException(vpImageException::ioError, "Cannot write file: Image format not supported"));
  }
#endif
  }
}

//--------------------------------------------------------------------------
// PFM
//--------------------------------------------------------------------------

void vpImageIo::writePFM(const vpImage<float> &I, const std::string &filename)
{
  FILE *fd;

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot write PFM image: filename empty"));
  }

  fd = fopen(filename.c_str(), "wb");

  if (fd == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PFM file \"%s\"", filename.c_str()));
  }

  // Write the head
  fprintf(fd, "P8\n");                                 // Magic number
  fprintf(fd, "%u %u\n", I.getWidth(), I.getHeight()); // Image size
  fprintf(fd, "255\n");                                // Max level

  // Write the bitmap
  size_t ierr;
  size_t nbyte = I.getWidth() * I.getHeight();

  ierr = fwrite(I.bitmap, sizeof(float), nbyte, fd);
  if (ierr != nbyte) {
    fclose(fd);
    throw(vpImageException(vpImageException::ioError, "Cannot save PFM file \"%s\": only %d bytes over %d saved ",
                           filename.c_str(), ierr, nbyte));
  }

  fflush(fd);
  fclose(fd);
}
//--------------------------------------------------------------------------
// PGM
//--------------------------------------------------------------------------

void vpImageIo::writePGM(const vpImage<unsigned char> &I, const std::string &filename)
{

  FILE *fd;

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PGM file: filename empty"));
  }

  fd = fopen(filename.c_str(), "wb");

  if (fd == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PGM file \"%s\"", filename.c_str()));
  }

  // Write the head
  fprintf(fd, "P5\n");                                 // Magic number
  fprintf(fd, "%u %u\n", I.getWidth(), I.getHeight()); // Image size
  fprintf(fd, "255\n");                                // Max level

  // Write the bitmap
  size_t ierr;
  size_t nbyte = I.getWidth() * I.getHeight();

  ierr = fwrite(I.bitmap, sizeof(unsigned char), nbyte, fd);
  if (ierr != nbyte) {
    fclose(fd);
    throw(vpImageException(vpImageException::ioError, "Cannot save PGM file \"%s\": only %d over %d bytes saved",
                           filename.c_str(), ierr, nbyte));
  }

  fflush(fd);
  fclose(fd);
}

void vpImageIo::writePGM(const vpImage<short> &I, const std::string &filename)
{
  vpImage<unsigned char> Iuc;
  unsigned int nrows = I.getHeight();
  unsigned int ncols = I.getWidth();

  Iuc.resize(nrows, ncols);

  for (unsigned int i = 0; i < nrows * ncols; i++)
    Iuc.bitmap[i] = (unsigned char)I.bitmap[i];

  vpImageIo::writePGM(Iuc, filename);
}
void vpImageIo::writePGM(const vpImage<vpRGBa> &I, const std::string &filename)
{

  FILE *fd;

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PGM file: filename empty"));
  }

  fd = fopen(filename.c_str(), "wb");

  if (fd == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PGM file \"%s\"", filename.c_str()));
  }

  // Write the head
  fprintf(fd, "P5\n");                                 // Magic number
  fprintf(fd, "%u %u\n", I.getWidth(), I.getHeight()); // Image size
  fprintf(fd, "255\n");                                // Max level

  // Write the bitmap
  size_t ierr;
  size_t nbyte = I.getWidth() * I.getHeight();

  vpImage<unsigned char> Itmp;
  vpImageConvert::convert(I, Itmp);

  ierr = fwrite(Itmp.bitmap, sizeof(unsigned char), nbyte, fd);
  if (ierr != nbyte) {
    fclose(fd);
    throw(vpImageException(vpImageException::ioError, "Cannot save PGM file \"%s\": only %d over %d bytes saved",
                           filename.c_str(), ierr, nbyte));
  }

  fflush(fd);
  fclose(fd);
}

void vpImageIo::readPFM(vpImage<float> &I, const std::string &filename)
{
  unsigned int w = 0, h = 0, maxval = 0;
  unsigned int w_max = 100000, h_max = 100000, maxval_max = 255;
  std::string magic("P8");

  std::ifstream fd(filename.c_str(), std::ios::binary);

  // Open the filename
  if (!fd.is_open()) {
    throw(vpImageException(vpImageException::ioError, "Cannot open file \"%s\"", filename.c_str()));
  }

  vp_decodeHeaderPNM(filename, fd, magic, w, h, maxval);

  if (w > w_max || h > h_max) {
    fd.close();
    throw(vpException(vpException::badValue, "Bad image size in \"%s\"", filename.c_str()));
  }
  if (maxval > maxval_max) {
    fd.close();
    throw(vpImageException(vpImageException::ioError, "Bad maxval in \"%s\"", filename.c_str()));
  }

  if ((h != I.getHeight()) || (w != I.getWidth())) {
    I.resize(h, w);
  }

  unsigned int nbyte = I.getHeight() * I.getWidth();
  fd.read((char *)I.bitmap, sizeof(float) * nbyte);
  if (!fd) {
    fd.close();
    throw(vpImageException(vpImageException::ioError, "Read only %d of %d bytes in file \"%s\"", fd.gcount(), nbyte,
                           filename.c_str()));
  }

  fd.close();
}

void vpImageIo::readPGM(vpImage<unsigned char> &I, const std::string &filename)
{
  unsigned int w = 0, h = 0, maxval = 0;
  unsigned int w_max = 100000, h_max = 100000, maxval_max = 255;
  std::string magic("P5");

  std::ifstream fd(filename.c_str(), std::ios::binary);

  // Open the filename
  if (!fd.is_open()) {
    throw(vpImageException(vpImageException::ioError, "Cannot open file \"%s\"", filename.c_str()));
  }

  vp_decodeHeaderPNM(filename, fd, magic, w, h, maxval);

  if (w > w_max || h > h_max) {
    fd.close();
    throw(vpException(vpException::badValue, "Bad image size in \"%s\"", filename.c_str()));
  }
  if (maxval > maxval_max) {
    fd.close();
    throw(vpImageException(vpImageException::ioError, "Bad maxval in \"%s\"", filename.c_str()));
  }

  if ((h != I.getHeight()) || (w != I.getWidth())) {
    I.resize(h, w);
  }

  unsigned int nbyte = I.getHeight() * I.getWidth();
  fd.read((char *)I.bitmap, nbyte);
  if (!fd) {
    fd.close();
    throw(vpImageException(vpImageException::ioError, "Read only %d of %d bytes in file \"%s\"", fd.gcount(), nbyte,
                           filename.c_str()));
  }

  fd.close();
}

void vpImageIo::readPGM(vpImage<vpRGBa> &I, const std::string &filename)
{
  vpImage<unsigned char> Itmp;

  vpImageIo::readPGM(Itmp, filename);

  vpImageConvert::convert(Itmp, I);
}

//--------------------------------------------------------------------------
// PPM
//--------------------------------------------------------------------------

void vpImageIo::readPPM(vpImage<unsigned char> &I, const std::string &filename)
{
  vpImage<vpRGBa> Itmp;

  vpImageIo::readPPM(Itmp, filename);

  vpImageConvert::convert(Itmp, I);
}

void vpImageIo::readPPM(vpImage<vpRGBa> &I, const std::string &filename)
{
  unsigned int w = 0, h = 0, maxval = 0;
  unsigned int w_max = 100000, h_max = 100000, maxval_max = 255;
  std::string magic("P6");

  std::ifstream fd(filename.c_str(), std::ios::binary);

  // Open the filename
  if (!fd.is_open()) {
    throw(vpImageException(vpImageException::ioError, "Cannot open file \"%s\"", filename.c_str()));
  }

  vp_decodeHeaderPNM(filename, fd, magic, w, h, maxval);

  if (w > w_max || h > h_max) {
    fd.close();
    throw(vpException(vpException::badValue, "Bad image size in \"%s\"", filename.c_str()));
  }
  if (maxval > maxval_max) {
    fd.close();
    throw(vpImageException(vpImageException::ioError, "Bad maxval in \"%s\"", filename.c_str()));
  }

  if ((h != I.getHeight()) || (w != I.getWidth())) {
    I.resize(h, w);
  }

  for (unsigned int i = 0; i < I.getHeight(); i++) {
    for (unsigned int j = 0; j < I.getWidth(); j++) {
      unsigned char rgb[3];
      fd.read((char *)&rgb, 3);

      if (!fd) {
        fd.close();
        throw(vpImageException(vpImageException::ioError, "Read only %d of %d bytes in file \"%s\"",
                               (i * I.getWidth() + j) * 3 + fd.gcount(), I.getSize() * 3, filename.c_str()));
      }

      I[i][j].R = rgb[0];
      I[i][j].G = rgb[1];
      I[i][j].B = rgb[2];
      I[i][j].A = vpRGBa::alpha_default;
    }
  }

  fd.close();
}

void vpImageIo::writePPM(const vpImage<unsigned char> &I, const std::string &filename)
{
  vpImage<vpRGBa> Itmp;

  vpImageConvert::convert(I, Itmp);

  vpImageIo::writePPM(Itmp, filename);
}

void vpImageIo::writePPM(const vpImage<vpRGBa> &I, const std::string &filename)
{
  FILE *f;

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PPM file: filename empty"));
  }

  f = fopen(filename.c_str(), "wb");

  if (f == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PPM file \"%s\"", filename.c_str()));
  }

  fprintf(f, "P6\n");                                 // Magic number
  fprintf(f, "%u %u\n", I.getWidth(), I.getHeight()); // Image size
  fprintf(f, "%d\n", 255);                            // Max level

  for (unsigned int i = 0; i < I.getHeight(); i++) {
    for (unsigned int j = 0; j < I.getWidth(); j++) {
      vpRGBa v = I[i][j];
      unsigned char rgb[3];
      rgb[0] = v.R;
      rgb[1] = v.G;
      rgb[2] = v.B;

      size_t res = fwrite(&rgb, 1, 3, f);
      if (res != 3) {
        fclose(f);
        throw(vpImageException(vpImageException::ioError, "cannot write file \"%s\"", filename.c_str()));
      }
    }
  }

  fflush(f);
  fclose(f);
}

//--------------------------------------------------------------------------
// JPEG
//--------------------------------------------------------------------------

#if defined(VISP_HAVE_JPEG)

void vpImageIo::writeJPEG(const vpImage<unsigned char> &I, const std::string &filename)
{
  struct jpeg_compress_struct cinfo;
  struct jpeg_error_mgr jerr;
  FILE *file;

  cinfo.err = jpeg_std_error(&jerr);
  jpeg_create_compress(&cinfo);

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot create JPEG file: filename empty"));
  }

  file = fopen(filename.c_str(), "wb");

  if (file == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot create JPEG file \"%s\"", filename.c_str()));
  }

  unsigned int width = I.getWidth();
  unsigned int height = I.getHeight();

  jpeg_stdio_dest(&cinfo, file);

  cinfo.image_width = width;
  cinfo.image_height = height;
  cinfo.input_components = 1;
  cinfo.in_color_space = JCS_GRAYSCALE;
  jpeg_set_defaults(&cinfo);

  jpeg_start_compress(&cinfo, TRUE);

  unsigned char *line;
  line = new unsigned char[width];
  unsigned char *input = (unsigned char *)I.bitmap;
  while (cinfo.next_scanline < cinfo.image_height) {
    for (unsigned int i = 0; i < width; i++) {
      line[i] = *(input);
      input++;
    }
    jpeg_write_scanlines(&cinfo, &line, 1);
  }

  jpeg_finish_compress(&cinfo);
  jpeg_destroy_compress(&cinfo);
  delete[] line;
  fclose(file);
}

void vpImageIo::writeJPEG(const vpImage<vpRGBa> &I, const std::string &filename)
{
  struct jpeg_compress_struct cinfo;
  struct jpeg_error_mgr jerr;
  FILE *file;

  cinfo.err = jpeg_std_error(&jerr);
  jpeg_create_compress(&cinfo);

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot create JPEG file: filename empty"));
  }

  file = fopen(filename.c_str(), "wb");

  if (file == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot create JPEG file \"%s\"", filename.c_str()));
  }

  unsigned int width = I.getWidth();
  unsigned int height = I.getHeight();

  jpeg_stdio_dest(&cinfo, file);

  cinfo.image_width = width;
  cinfo.image_height = height;
  cinfo.input_components = 3;
  cinfo.in_color_space = JCS_RGB;
  jpeg_set_defaults(&cinfo);

  jpeg_start_compress(&cinfo, TRUE);

  unsigned char *line;
  line = new unsigned char[3 * width];
  unsigned char *input = (unsigned char *)I.bitmap;
  while (cinfo.next_scanline < cinfo.image_height) {
    for (unsigned int i = 0; i < width; i++) {
      line[i * 3] = *(input);
      input++;
      line[i * 3 + 1] = *(input);
      input++;
      line[i * 3 + 2] = *(input);
      input++;
      input++;
    }
    jpeg_write_scanlines(&cinfo, &line, 1);
  }

  jpeg_finish_compress(&cinfo);
  jpeg_destroy_compress(&cinfo);
  delete[] line;
  fclose(file);
}

void vpImageIo::readJPEG(vpImage<unsigned char> &I, const std::string &filename)
{
  struct jpeg_decompress_struct cinfo;
  struct jpeg_error_mgr jerr;
  FILE *file;

  cinfo.err = jpeg_std_error(&jerr);
  jpeg_create_decompress(&cinfo);

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot read JPEG image: filename empty"));
  }

  file = fopen(filename.c_str(), "rb");

  if (file == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot read JPEG file \"%s\"", filename.c_str()));
  }

  jpeg_stdio_src(&cinfo, file);
  jpeg_read_header(&cinfo, TRUE);

  unsigned int width = cinfo.image_width;
  unsigned int height = cinfo.image_height;

  if ((width != I.getWidth()) || (height != I.getHeight()))
    I.resize(height, width);

  jpeg_start_decompress(&cinfo);

  unsigned int rowbytes = cinfo.output_width * (unsigned int)(cinfo.output_components);
  JSAMPARRAY buffer = (*cinfo.mem->alloc_sarray)((j_common_ptr)&cinfo, JPOOL_IMAGE, rowbytes, 1);

  if (cinfo.out_color_space == JCS_RGB) {
    vpImage<vpRGBa> Ic(height, width);
    unsigned char *output = (unsigned char *)Ic.bitmap;
    while (cinfo.output_scanline < cinfo.output_height) {
      jpeg_read_scanlines(&cinfo, buffer, 1);
      for (unsigned int i = 0; i < width; i++) {
        *(output++) = buffer[0][i * 3];
        *(output++) = buffer[0][i * 3 + 1];
        *(output++) = buffer[0][i * 3 + 2];
        *(output++) = vpRGBa::alpha_default;
      }
    }
    vpImageConvert::convert(Ic, I);
  }

  else if (cinfo.out_color_space == JCS_GRAYSCALE) {
    while (cinfo.output_scanline < cinfo.output_height) {
      unsigned int row = cinfo.output_scanline;
      jpeg_read_scanlines(&cinfo, buffer, 1);
      memcpy(I[row], buffer[0], rowbytes);
    }
  }

  jpeg_finish_decompress(&cinfo);
  jpeg_destroy_decompress(&cinfo);
  fclose(file);
}

void vpImageIo::readJPEG(vpImage<vpRGBa> &I, const std::string &filename)
{
  struct jpeg_decompress_struct cinfo;
  struct jpeg_error_mgr jerr;
  FILE *file;

  cinfo.err = jpeg_std_error(&jerr);
  jpeg_create_decompress(&cinfo);

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot read JPEG image: filename empty"));
  }

  file = fopen(filename.c_str(), "rb");

  if (file == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot read JPEG file \"%s\"", filename.c_str()));
  }

  jpeg_stdio_src(&cinfo, file);

  jpeg_read_header(&cinfo, TRUE);

  unsigned int width = cinfo.image_width;
  unsigned int height = cinfo.image_height;

  if ((width != I.getWidth()) || (height != I.getHeight()))
    I.resize(height, width);

  jpeg_start_decompress(&cinfo);

  unsigned int rowbytes = cinfo.output_width * (unsigned int)(cinfo.output_components);
  JSAMPARRAY buffer = (*cinfo.mem->alloc_sarray)((j_common_ptr)&cinfo, JPOOL_IMAGE, rowbytes, 1);

  if (cinfo.out_color_space == JCS_RGB) {
    unsigned char *output = (unsigned char *)I.bitmap;
    while (cinfo.output_scanline < cinfo.output_height) {
      jpeg_read_scanlines(&cinfo, buffer, 1);
      for (unsigned int i = 0; i < width; i++) {
        *(output++) = buffer[0][i * 3];
        *(output++) = buffer[0][i * 3 + 1];
        *(output++) = buffer[0][i * 3 + 2];
        *(output++) = vpRGBa::alpha_default;
      }
    }
  }

  else if (cinfo.out_color_space == JCS_GRAYSCALE) {
    vpImage<unsigned char> Ig(height, width);

    while (cinfo.output_scanline < cinfo.output_height) {
      unsigned int row = cinfo.output_scanline;
      jpeg_read_scanlines(&cinfo, buffer, 1);
      memcpy(Ig[row], buffer[0], rowbytes);
    }

    vpImageConvert::convert(Ig, I);
  }

  jpeg_finish_decompress(&cinfo);
  jpeg_destroy_decompress(&cinfo);
  fclose(file);
}

#elif defined(VISP_HAVE_OPENCV)

void vpImageIo::writeJPEG(const vpImage<unsigned char> &I, const std::string &filename)
{
#if (VISP_HAVE_OPENCV_VERSION >= 0x020408)
  cv::Mat Ip;
  vpImageConvert::convert(I, Ip);
  cv::imwrite(filename.c_str(), Ip);
#else
  IplImage *Ip = NULL;
  vpImageConvert::convert(I, Ip);

  cvSaveImage(filename.c_str(), Ip);

  cvReleaseImage(&Ip);
#endif
}

void vpImageIo::writeJPEG(const vpImage<vpRGBa> &I, const std::string &filename)
{
#if (VISP_HAVE_OPENCV_VERSION >= 0x020408)
  cv::Mat Ip;
  vpImageConvert::convert(I, Ip);
  cv::imwrite(filename.c_str(), Ip);
#else
  IplImage *Ip = NULL;
  vpImageConvert::convert(I, Ip);

  cvSaveImage(filename.c_str(), Ip);

  cvReleaseImage(&Ip);
#endif
}

void vpImageIo::readJPEG(vpImage<unsigned char> &I, const std::string &filename)
{
#if defined(VISP_HAVE_OPENCV) && VISP_HAVE_OPENCV_VERSION >= 0x020100
#if VISP_HAVE_OPENCV_VERSION >= 0x030200
    int flags = cv::IMREAD_GRAYSCALE | cv::IMREAD_IGNORE_ORIENTATION;
#elif VISP_HAVE_OPENCV_VERSION >= 0x030000
    int flags = cv::IMREAD_GRAYSCALE;
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
    int flags = CV_LOAD_IMAGE_GRAYSCALE;
#endif
  cv::Mat Ip = cv::imread(filename.c_str(), flags);
  if (!Ip.empty())
    vpImageConvert::convert(Ip, I);
  else
    throw(vpImageException(vpImageException::ioError, "Can't read the image"));
#else
  IplImage *Ip = NULL;
  Ip = cvLoadImage(filename.c_str(), CV_LOAD_IMAGE_GRAYSCALE);
  if (Ip != NULL)
    vpImageConvert::convert(Ip, I);
  else
    throw(vpImageException(vpImageException::ioError, "Can't read the image"));
  cvReleaseImage(&Ip);
#endif
}

void vpImageIo::readJPEG(vpImage<vpRGBa> &I, const std::string &filename)
{
#if defined(VISP_HAVE_OPENCV) && VISP_HAVE_OPENCV_VERSION >= 0x020100
#if VISP_HAVE_OPENCV_VERSION >= 0x030200
    int flags = cv::IMREAD_GRAYSCALE | cv::IMREAD_IGNORE_ORIENTATION;
#elif VISP_HAVE_OPENCV_VERSION >= 0x030000
    int flags = cv::IMREAD_GRAYSCALE;
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
    int flags = CV_LOAD_IMAGE_GRAYSCALE;
#endif
  cv::Mat Ip = cv::imread(filename.c_str(), flags);
  if (!Ip.empty())
    vpImageConvert::convert(Ip, I);
  else
    throw(vpImageException(vpImageException::ioError, "Can't read the image"));
#else
  IplImage *Ip = NULL;
  Ip = cvLoadImage(filename.c_str(), CV_LOAD_IMAGE_COLOR);
  if (Ip != NULL)
    vpImageConvert::convert(Ip, I);
  else
    throw(vpImageException(vpImageException::ioError, "Can't read the image"));
  cvReleaseImage(&Ip);
#endif
}
#else
void vpImageIo::readJPEG(vpImage<unsigned char> &I, const std::string &filename)
{
  int width = 0, height = 0, channels = 0;
  unsigned char *image = stbi_load(filename.c_str(), &width, &height, &channels, STBI_grey);
  if (image == NULL) {
    throw(vpImageException(vpImageException::ioError, "Can't read the image: %s", filename.c_str()));
  }
  I.init(image, static_cast<unsigned int>(height), static_cast<unsigned int>(width), true);
  stbi_image_free(image);
}
void vpImageIo::readJPEG(vpImage<vpRGBa> &I, const std::string &filename)
{
  int width = 0, height = 0, channels = 0;
  unsigned char *image = stbi_load(filename.c_str(), &width, &height, &channels, STBI_rgb_alpha);
  if (image == NULL) {
    throw(vpImageException(vpImageException::ioError, "Can't read the image: %s", filename.c_str()));
  }
  I.init(reinterpret_cast<vpRGBa*>(image), static_cast<unsigned int>(height), static_cast<unsigned int>(width), true);
  stbi_image_free(image);
}
void vpImageIo::writeJPEG(const vpImage<unsigned char> &I, const std::string &filename)
{
  int res = stbi_write_jpg(filename.c_str(), static_cast<int>(I.getWidth()), static_cast<int>(I.getHeight()), STBI_grey,
                           reinterpret_cast<void*>(I.bitmap), 90);
  if (res == 0) {
    throw(vpImageException(vpImageException::ioError, "JPEG write error"));
  }
}
void vpImageIo::writeJPEG(const vpImage<vpRGBa> &I, const std::string &filename)
{
  int res = stbi_write_jpg(filename.c_str(), static_cast<int>(I.getWidth()), static_cast<int>(I.getHeight()), STBI_rgb_alpha,
                           reinterpret_cast<void*>(I.bitmap), 90);
  if (res == 0) {
    throw(vpImageException(vpImageException::ioError, "JEPG write error"));
  }
}
#endif

//--------------------------------------------------------------------------
// PNG
//--------------------------------------------------------------------------

#if defined(VISP_HAVE_PNG)

void vpImageIo::writePNG(const vpImage<unsigned char> &I, const std::string &filename)
{
  FILE *file;

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PNG file: filename empty"));
  }

  file = fopen(filename.c_str(), "wb");

  if (file == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PNG file \"%s\"", filename.c_str()));
  }

  /* create a png info struct */
  png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
  if (!png_ptr) {
    fclose(file);
    vpERROR_TRACE("Error during png_create_write_struct()\n");
    throw(vpImageException(vpImageException::ioError, "PNG write error"));
  }

  png_infop info_ptr = png_create_info_struct(png_ptr);
  if (!info_ptr) {
    fclose(file);
    png_destroy_write_struct(&png_ptr, NULL);
    vpERROR_TRACE("Error during png_create_info_struct()\n");
    throw(vpImageException(vpImageException::ioError, "PNG write error"));
  }

  /* initialize the setjmp for returning properly after a libpng error occured
   */
  if (setjmp(png_jmpbuf(png_ptr))) {
    fclose(file);
    png_destroy_write_struct(&png_ptr, &info_ptr);
    vpERROR_TRACE("Error during init_io\n");
    throw(vpImageException(vpImageException::ioError, "PNG write error"));
  }

  /* setup libpng for using standard C fwrite() function with our FILE pointer
   */
  png_init_io(png_ptr, file);

  unsigned int width = I.getWidth();
  unsigned int height = I.getHeight();
  int bit_depth = 8;
  int color_type = PNG_COLOR_TYPE_GRAY;
  /* set some useful information from header */

  if (setjmp(png_jmpbuf(png_ptr))) {
    fclose(file);
    png_destroy_write_struct(&png_ptr, &info_ptr);
    vpERROR_TRACE("Error during write header\n");
    throw(vpImageException(vpImageException::ioError, "PNG write error"));
  }

  png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, color_type, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
               PNG_FILTER_TYPE_BASE);

  png_write_info(png_ptr, info_ptr);

  png_bytep *row_ptrs = new png_bytep[height];
  for (unsigned int i = 0; i < height; i++)
    row_ptrs[i] = new png_byte[width];

  unsigned char *input = (unsigned char *)I.bitmap;

  for (unsigned int i = 0; i < height; i++) {
    png_byte *row = row_ptrs[i];
    for (unsigned int j = 0; j < width; j++) {
      row[j] = *(input);
      input++;
    }
  }

  png_write_image(png_ptr, row_ptrs);

  png_write_end(png_ptr, NULL);

  for (unsigned int j = 0; j < height; j++)
    delete[] row_ptrs[j];

  delete[] row_ptrs;

  png_destroy_write_struct(&png_ptr, &info_ptr);

  fclose(file);
}

void vpImageIo::writePNG(const vpImage<vpRGBa> &I, const std::string &filename)
{
  FILE *file;

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PNG file: filename empty"));
  }

  file = fopen(filename.c_str(), "wb");

  if (file == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot create PNG file \"%s\"", filename.c_str()));
  }

  /* create a png info struct */
  png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
  if (!png_ptr) {
    fclose(file);
    vpERROR_TRACE("Error during png_create_write_struct()\n");
    throw(vpImageException(vpImageException::ioError, "PNG write error"));
  }

  png_infop info_ptr = png_create_info_struct(png_ptr);
  if (!info_ptr) {
    fclose(file);
    png_destroy_write_struct(&png_ptr, NULL);
    vpERROR_TRACE("Error during png_create_info_struct()\n");
    throw(vpImageException(vpImageException::ioError, "PNG write error"));
  }

  /* initialize the setjmp for returning properly after a libpng error occured
   */
  if (setjmp(png_jmpbuf(png_ptr))) {
    fclose(file);
    png_destroy_write_struct(&png_ptr, &info_ptr);
    vpERROR_TRACE("Error during init_io\n");
    throw(vpImageException(vpImageException::ioError, "PNG write error"));
  }

  /* setup libpng for using standard C fwrite() function with our FILE pointer
   */
  png_init_io(png_ptr, file);

  unsigned int width = I.getWidth();
  unsigned int height = I.getHeight();
  int bit_depth = 8;
  int color_type = PNG_COLOR_TYPE_RGB;
  /* set some useful information from header */

  if (setjmp(png_jmpbuf(png_ptr))) {
    fclose(file);
    png_destroy_write_struct(&png_ptr, &info_ptr);
    vpERROR_TRACE("Error during write header\n");
    throw(vpImageException(vpImageException::ioError, "PNG write error"));
  }

  png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, color_type, PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
               PNG_FILTER_TYPE_BASE);

  png_write_info(png_ptr, info_ptr);

  png_bytep *row_ptrs = new png_bytep[height];
  for (unsigned int i = 0; i < height; i++)
    row_ptrs[i] = new png_byte[3 * width];

  unsigned char *input = (unsigned char *)I.bitmap;
  ;

  for (unsigned int i = 0; i < height; i++) {
    png_byte *row = row_ptrs[i];
    for (unsigned int j = 0; j < width; j++) {
      row[3 * j] = *(input);
      input++;
      row[3 * j + 1] = *(input);
      input++;
      row[3 * j + 2] = *(input);
      input++;
      input++;
    }
  }

  png_write_image(png_ptr, row_ptrs);

  png_write_end(png_ptr, NULL);

  for (unsigned int j = 0; j < height; j++)
    delete[] row_ptrs[j];

  delete[] row_ptrs;

  png_destroy_write_struct(&png_ptr, &info_ptr);

  fclose(file);
}

void vpImageIo::readPNG(vpImage<unsigned char> &I, const std::string &filename)
{
  FILE *file;
  png_byte magic[8];
  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot read PNG image: filename empty"));
  }

  file = fopen(filename.c_str(), "rb");

  if (file == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot read file \"%s\"", filename.c_str()));
  }

  /* read magic number */
  if (fread(magic, 1, sizeof(magic), file) != sizeof(magic)) {
    fclose(file);
    throw(vpImageException(vpImageException::ioError, "Cannot read magic number in file \"%s\"", filename.c_str()));
  }

  /* check for valid magic number */
  if (png_sig_cmp(magic, 0, sizeof(magic))) {
    fclose(file);
    throw(vpImageException(vpImageException::ioError, "Cannot read PNG file: \"%s\" is not a valid PNG image",
                           filename.c_str()));
  }

  /* create a png read struct */
  // printf("version %s\n", PNG_LIBPNG_VER_STRING);
  png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
  if (png_ptr == NULL) {
    fprintf(stderr, "error: can't create a png read structure!\n");
    fclose(file);
    throw(vpImageException(vpImageException::ioError, "error reading png file"));
  }

  /* create a png info struct */
  png_infop info_ptr = png_create_info_struct(png_ptr);
  if (info_ptr == NULL) {
    fprintf(stderr, "error: can't create a png info structure!\n");
    fclose(file);
    png_destroy_read_struct(&png_ptr, NULL, NULL);
    throw(vpImageException(vpImageException::ioError, "error reading png file"));
  }

  /* initialize the setjmp for returning properly after a libpng error occured
   */
  if (setjmp(png_jmpbuf(png_ptr))) {
    fclose(file);
    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
    vpERROR_TRACE("Error during init io\n");
    throw(vpImageException(vpImageException::ioError, "PNG read error"));
  }

  /* setup libpng for using standard C fread() function with our FILE pointer
   */
  png_init_io(png_ptr, file);

  /* tell libpng that we have already read the magic number */
  png_set_sig_bytes(png_ptr, sizeof(magic));

  /* read png info */
  png_read_info(png_ptr, info_ptr);

  unsigned int width = png_get_image_width(png_ptr, info_ptr);
  unsigned int height = png_get_image_height(png_ptr, info_ptr);

  unsigned int bit_depth, channels, color_type;
  /* get some useful information from header */
  bit_depth = png_get_bit_depth(png_ptr, info_ptr);
  channels = png_get_channels(png_ptr, info_ptr);
  color_type = png_get_color_type(png_ptr, info_ptr);

  /* convert index color images to RGB images */
  if (color_type == PNG_COLOR_TYPE_PALETTE)
    png_set_palette_to_rgb(png_ptr);

  /* convert 1-2-4 bits grayscale images to 8 bits grayscale. */
  if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
    png_set_expand(png_ptr);

  //  if (png_get_valid (png_ptr, info_ptr, PNG_INFO_tRNS))
  //    png_set_tRNS_to_alpha (png_ptr);

  if (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
    png_set_strip_alpha(png_ptr);

  if (bit_depth == 16)
    png_set_strip_16(png_ptr);
  else if (bit_depth < 8)
    png_set_packing(png_ptr);

  /* update info structure to apply transformations */
  png_read_update_info(png_ptr, info_ptr);

  channels = png_get_channels(png_ptr, info_ptr);

  if ((width != I.getWidth()) || (height != I.getHeight()))
    I.resize(height, width);

  png_bytep *rowPtrs = new png_bytep[height];

  unsigned int stride = png_get_rowbytes(png_ptr, info_ptr);
  unsigned char *data = new unsigned char[stride * height];

  for (unsigned int i = 0; i < height; i++)
    rowPtrs[i] = (png_bytep)data + (i * stride);

  png_read_image(png_ptr, rowPtrs);

  vpImage<vpRGBa> Ic(height, width);
  unsigned char *output;

  switch (channels) {
  case 1:
    output = (unsigned char *)I.bitmap;
    for (unsigned int i = 0; i < width * height; i++) {
      *(output++) = data[i];
    }
    break;

  case 2:
    output = (unsigned char *)I.bitmap;
    for (unsigned int i = 0; i < width * height; i++) {
      *(output++) = data[i * 2];
    }
    break;

  case 3:
    output = (unsigned char *)Ic.bitmap;
    for (unsigned int i = 0; i < width * height; i++) {
      *(output++) = data[i * 3];
      *(output++) = data[i * 3 + 1];
      *(output++) = data[i * 3 + 2];
      *(output++) = vpRGBa::alpha_default;
    }
    vpImageConvert::convert(Ic, I);
    break;

  case 4:
    output = (unsigned char *)Ic.bitmap;
    for (unsigned int i = 0; i < width * height; i++) {
      *(output++) = data[i * 4];
      *(output++) = data[i * 4 + 1];
      *(output++) = data[i * 4 + 2];
      *(output++) = data[i * 4 + 3];
    }
    vpImageConvert::convert(Ic, I);
    break;
  }

  delete[](png_bytep) rowPtrs;
  delete[] data;
  png_read_end(png_ptr, NULL);
  png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
  fclose(file);
}

void vpImageIo::readPNG(vpImage<vpRGBa> &I, const std::string &filename)
{
  FILE *file;
  png_byte magic[8];

  // Test the filename
  if (filename.empty()) {
    throw(vpImageException(vpImageException::ioError, "Cannot read PNG image: filename empty"));
  }

  file = fopen(filename.c_str(), "rb");

  if (file == NULL) {
    throw(vpImageException(vpImageException::ioError, "Cannot read file \"%s\"", filename.c_str()));
  }

  /* read magic number */
  if (fread(magic, 1, sizeof(magic), file) != sizeof(magic)) {
    fclose(file);
    throw(vpImageException(vpImageException::ioError, "Cannot read magic number in file \"%s\"", filename.c_str()));
  }

  /* check for valid magic number */
  if (png_sig_cmp(magic, 0, sizeof(magic))) {
    fclose(file);
    throw(vpImageException(vpImageException::ioError, "Cannot read PNG file: \"%s\" is not a valid PNG image",
                           filename.c_str()));
  }

  /* create a png read struct */
  png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
  if (!png_ptr) {
    fclose(file);
    vpERROR_TRACE("Error during png_create_read_struct()\n");
    throw(vpImageException(vpImageException::ioError, "PNG read error"));
  }

  /* create a png info struct */
  png_infop info_ptr = png_create_info_struct(png_ptr);
  if (!info_ptr) {
    fclose(file);
    png_destroy_read_struct(&png_ptr, NULL, NULL);
    vpERROR_TRACE("Error during png_create_info_struct()\n");
    throw(vpImageException(vpImageException::ioError, "PNG read error"));
  }

  /* initialize the setjmp for returning properly after a libpng error occured
   */
  if (setjmp(png_jmpbuf(png_ptr))) {
    fclose(file);
    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
    vpERROR_TRACE("Error during init io\n");
    throw(vpImageException(vpImageException::ioError, "PNG read error"));
  }

  /* setup libpng for using standard C fread() function with our FILE pointer
   */
  png_init_io(png_ptr, file);

  /* tell libpng that we have already read the magic number */
  png_set_sig_bytes(png_ptr, sizeof(magic));

  /* read png info */
  png_read_info(png_ptr, info_ptr);

  unsigned int width = png_get_image_width(png_ptr, info_ptr);
  unsigned int height = png_get_image_height(png_ptr, info_ptr);

  unsigned int bit_depth, channels, color_type;
  /* get some useful information from header */
  bit_depth = png_get_bit_depth(png_ptr, info_ptr);
  channels = png_get_channels(png_ptr, info_ptr);
  color_type = png_get_color_type(png_ptr, info_ptr);

  /* convert index color images to RGB images */
  if (color_type == PNG_COLOR_TYPE_PALETTE)
    png_set_palette_to_rgb(png_ptr);

  /* convert 1-2-4 bits grayscale images to 8 bits grayscale. */
  if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
    png_set_expand(png_ptr);

  //  if (png_get_valid (png_ptr, info_ptr, PNG_INFO_tRNS))
  //    png_set_tRNS_to_alpha (png_ptr);

  if (color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
    png_set_strip_alpha(png_ptr);

  if (bit_depth == 16)
    png_set_strip_16(png_ptr);
  else if (bit_depth < 8)
    png_set_packing(png_ptr);

  /* update info structure to apply transformations */
  png_read_update_info(png_ptr, info_ptr);

  channels = png_get_channels(png_ptr, info_ptr);

  if ((width != I.getWidth()) || (height != I.getHeight()))
    I.resize(height, width);

  png_bytep *rowPtrs = new png_bytep[height];

  unsigned int stride = png_get_rowbytes(png_ptr, info_ptr);
  unsigned char *data = new unsigned char[stride * height];

  for (unsigned int i = 0; i < height; i++)
    rowPtrs[i] = (png_bytep)data + (i * stride);

  png_read_image(png_ptr, rowPtrs);

  vpImage<unsigned char> Ig(height, width);
  unsigned char *output;

  switch (channels) {
  case 1:
    output = (unsigned char *)Ig.bitmap;
    for (unsigned int i = 0; i < width * height; i++) {
      *(output++) = data[i];
    }
    vpImageConvert::convert(Ig, I);
    break;

  case 2:
    output = (unsigned char *)Ig.bitmap;
    for (unsigned int i = 0; i < width * height; i++) {
      *(output++) = data[i * 2];
    }
    vpImageConvert::convert(Ig, I);
    break;

  case 3:
    output = (unsigned char *)I.bitmap;
    for (unsigned int i = 0; i < width * height; i++) {
      *(output++) = data[i * 3];
      *(output++) = data[i * 3 + 1];
      *(output++) = data[i * 3 + 2];
      *(output++) = vpRGBa::alpha_default;
    }
    break;

  case 4:
    output = (unsigned char *)I.bitmap;
    for (unsigned int i = 0; i < width * height; i++) {
      *(output++) = data[i * 4];
      *(output++) = data[i * 4 + 1];
      *(output++) = data[i * 4 + 2];
      *(output++) = data[i * 4 + 3];
    }
    break;
  }

  delete[](png_bytep) rowPtrs;
  delete[] data;
  png_read_end(png_ptr, NULL);
  png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
  fclose(file);
}

#elif defined(VISP_HAVE_OPENCV)

void vpImageIo::writePNG(const vpImage<unsigned char> &I, const std::string &filename)
{
#if (VISP_HAVE_OPENCV_VERSION >= 0x020408)
  cv::Mat Ip;
  vpImageConvert::convert(I, Ip);
  cv::imwrite(filename.c_str(), Ip);
#else
  IplImage *Ip = NULL;
  vpImageConvert::convert(I, Ip);

  cvSaveImage(filename.c_str(), Ip);

  cvReleaseImage(&Ip);
#endif
}

void vpImageIo::writePNG(const vpImage<vpRGBa> &I, const std::string &filename)
{
#if (VISP_HAVE_OPENCV_VERSION >= 0x020408)
  cv::Mat Ip;
  vpImageConvert::convert(I, Ip);
  cv::imwrite(filename.c_str(), Ip);
#else
  IplImage *Ip = NULL;
  vpImageConvert::convert(I, Ip);

  cvSaveImage(filename.c_str(), Ip);

  cvReleaseImage(&Ip);
#endif
}

void vpImageIo::readPNG(vpImage<unsigned char> &I, const std::string &filename)
{
#if defined(VISP_HAVE_OPENCV) && VISP_HAVE_OPENCV_VERSION >= 0x020100
#if VISP_HAVE_OPENCV_VERSION >= 0x030200
    int flags = cv::IMREAD_GRAYSCALE | cv::IMREAD_IGNORE_ORIENTATION;
#elif VISP_HAVE_OPENCV_VERSION >= 0x030000
    int flags = cv::IMREAD_GRAYSCALE;
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
    int flags = CV_LOAD_IMAGE_GRAYSCALE;
#endif
  cv::Mat Ip = cv::imread(filename.c_str(), flags);
  if (!Ip.empty())
    vpImageConvert::convert(Ip, I);
  else
    throw(vpImageException(vpImageException::ioError, "Can't read the image"));
#else
  IplImage *Ip = NULL;
  Ip = cvLoadImage(filename.c_str(), CV_LOAD_IMAGE_GRAYSCALE);
  if (Ip != NULL)
    vpImageConvert::convert(Ip, I);
  else
    throw(vpImageException(vpImageException::ioError, "Can't read the image"));
  cvReleaseImage(&Ip);
#endif
}

void vpImageIo::readPNG(vpImage<vpRGBa> &I, const std::string &filename)
{
#if defined(VISP_HAVE_OPENCV) && VISP_HAVE_OPENCV_VERSION >= 0x020100
#if VISP_HAVE_OPENCV_VERSION >= 0x030200
    int flags = cv::IMREAD_COLOR | cv::IMREAD_IGNORE_ORIENTATION;
#elif VISP_HAVE_OPENCV_VERSION >= 0x030000
    int flags = cv::IMREAD_COLOR;
#elif VISP_HAVE_OPENCV_VERSION >= 0x020100
    int flags = CV_LOAD_IMAGE_COLOR;
#endif
  cv::Mat Ip = cv::imread(filename.c_str(), flags);
  if (!Ip.empty())
    vpImageConvert::convert(Ip, I);
  else
    throw(vpImageException(vpImageException::ioError, "Can't read the image"));
#else
  IplImage *Ip = NULL;
  Ip = cvLoadImage(filename.c_str(), CV_LOAD_IMAGE_COLOR);
  if (Ip != NULL)
    vpImageConvert::convert(Ip, I);
  else
    throw(vpImageException(vpImageException::ioError, "Can't read the image"));
  cvReleaseImage(&Ip);
#endif
}
#else
void vpImageIo::readPNG(vpImage<unsigned char> &I, const std::string &filename)
{
  int width = 0, height = 0, channels = 0;
  unsigned char *image = stbi_load(filename.c_str(), &width, &height, &channels, STBI_grey);
  if (image == NULL) {
    throw(vpImageException(vpImageException::ioError, "Can't read the image: %s", filename.c_str()));
  }
  I.init(image, static_cast<unsigned int>(height), static_cast<unsigned int>(width), true);
  stbi_image_free(image);
}
void vpImageIo::readPNG(vpImage<vpRGBa> &I, const std::string &filename)
{
  int width = 0, height = 0, channels = 0;
  unsigned char *image = stbi_load(filename.c_str(), &width, &height, &channels, STBI_rgb_alpha);
  if (image == NULL) {
    throw(vpImageException(vpImageException::ioError, "Can't read the image: %s", filename.c_str()));
  }
  I.init(reinterpret_cast<vpRGBa*>(image), static_cast<unsigned int>(height), static_cast<unsigned int>(width), true);
  stbi_image_free(image);
}
void vpImageIo::writePNG(const vpImage<unsigned char> &I, const std::string &filename)
{
  const int stride_in_bytes = static_cast<int>(I.getWidth());
  int res = stbi_write_png(filename.c_str(), static_cast<int>(I.getWidth()), static_cast<int>(I.getHeight()), STBI_grey,
                           reinterpret_cast<void*>(I.bitmap), stride_in_bytes);
  if (res == 0) {
    throw(vpImageException(vpImageException::ioError, "PNG write error: %s", filename.c_str()));
  }
}
void vpImageIo::writePNG(const vpImage<vpRGBa> &I, const std::string &filename)
{
  const int stride_in_bytes = static_cast<int>(4 * I.getWidth());
  int res = stbi_write_png(filename.c_str(), static_cast<int>(I.getWidth()), static_cast<int>(I.getHeight()), STBI_rgb_alpha,
                           reinterpret_cast<void*>(I.bitmap), stride_in_bytes);
  if (res == 0) {
    throw(vpImageException(vpImageException::ioError, "PNG write error: %s", filename.c_str()));
  }
}
#endif