vpCannyEdgeDetection.h

/*
 * ViSP, open source Visual Servoing Platform software.
 * Copyright (C) 2005 - 2025 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 https://visp.inria.fr for more information.
 *
 * This software was developed at:
 * Inria Rennes - Bretagne Atlantique
 * Campus Universitaire de Beaulieu
 * 35042 Rennes Cedex
 * France
 *
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 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */
 
#ifndef VP_CANNY_EDGE_DETECTION_H
#define VP_CANNY_EDGE_DETECTION_H
 
// System includes
#include <map>
#include <vector>
#include <iostream>
#if !defined(_WIN32) && (defined(__unix__) || defined(__unix) || (defined(__APPLE__) && defined(__MACH__))) // UNIX
#include <sys/resource.h> // To dynamically change the stack size
#endif
 
// ViSP include
#include <visp3/core/vpConfig.h>
#if (VISP_CXX_STANDARD >= VISP_CXX_STANDARD_11)
#include <visp3/core/vpHSV.h>
#endif
#include <visp3/core/vpImage.h>
#include <visp3/core/vpImageFilter.h>
#include <visp3/core/vpRGBa.h>
 
// 3rd parties include
#ifdef VISP_HAVE_NLOHMANN_JSON
#include VISP_NLOHMANN_JSON(json.hpp)
#endif
 
BEGIN_VISP_NAMESPACE
class VISP_EXPORT vpCannyEdgeDetection
{
 
public:

  vpCannyEdgeDetection();

  vpCannyEdgeDetection(const int &gaussianKernelSize, const float &gaussianStdev, const unsigned int &sobelAperture,
                       const float &lowerThreshold = -1.f, const float &upperThreshold = -1.f,
                       const float &lowerThresholdRatio = 0.6f, const float &upperThresholdRatio = 0.8f,
                       const vpImageFilter::vpCannyFilteringAndGradientType &filteringType = vpImageFilter::CANNY_GBLUR_SOBEL_FILTERING,
                       const bool &storeEdgePoints = false, const int &nbThread = -1);

  void reinit();
 
  // // Configuration from files
#ifdef VISP_HAVE_NLOHMANN_JSON
  vpCannyEdgeDetection(const std::string &jsonPath);

  void initFromJSON(const std::string &jsonPath);

  friend void from_json(const nlohmann::json &j, vpCannyEdgeDetection &detector);

  friend void to_json(nlohmann::json &j, const vpCannyEdgeDetection &detector);
#endif

#ifdef HAVE_OPENCV_CORE
  vpImage<unsigned char> detect(const cv::Mat &cv_I);
#endif

  vpImage<unsigned char> detect(const vpImage<vpRGBa> &I_color);
 
#if (VISP_CXX_STANDARD >= VISP_CXX_STANDARD_11)
  template <typename ArithmeticType, bool useFullScale>
  vpImage<unsigned char> detect(const vpImage<vpHSV<ArithmeticType, useFullScale>> &Ihsv)
  {
    // // Step 1 and 2: filter the image and compute the gradient, if not given by the user
    if (!m_areGradientAvailable) {
      vpImage<vpHSV<ArithmeticType, useFullScale>> Iblur;
      vpImageFilter::gaussianBlur(Ihsv, Iblur, m_gaussianKernelSize, m_gaussianStdev, true, mp_mask);
      vpImageFilter::gradientFilter(Iblur, m_dIx, m_dIy, m_nbThread, mp_mask, m_filteringAndGradientType);
    }
    m_areGradientAvailable = false; // Reset for next call
 
    // // Step 3: edge thining
    float upperThreshold = m_upperThreshold;
    float lowerThreshold = m_lowerThreshold;
    if (upperThreshold < 0) {
      upperThreshold = vpImageFilter::computeCannyThreshold(Ihsv, lowerThreshold, &m_dIx, &m_dIy, m_gaussianKernelSize,
                                                            m_gaussianStdev, m_lowerThresholdRatio,
                                                            m_upperThresholdRatio, m_filteringAndGradientType, mp_mask);
    }
    else if (m_lowerThreshold < 0) {
      // Applying Canny recommendation to have the upper threshold 3 times greater than the lower threshold.
      lowerThreshold = m_upperThreshold / 3.f;
    }
    // To ensure that if lowerThreshold = 0, we reject null gradient points
    lowerThreshold = std::max<float>(lowerThreshold, std::numeric_limits<float>::epsilon());
 
    step3to5(Ihsv.getHeight(), Ihsv.getWidth(), lowerThreshold, upperThreshold);
    return m_edgeMap;
  }
#endif

  vpImage<unsigned char> detect(const vpImage<unsigned char> &I);


  inline void setFilteringAndGradientType(const vpImageFilter::vpCannyFilteringAndGradientType &type)
  {
    m_filteringAndGradientType = type;
    initGradientFilters();
  }

  inline void setGradients(const vpImage<float> &dIx, const vpImage<float> &dIy)
  {
    m_dIx = dIx;
    m_dIy = dIy;
    m_areGradientAvailable = true;
  }

  inline void setCannyThresholds(const float &lowerThresh, const float &upperThresh)
  {
    m_lowerThreshold = lowerThresh;
    m_upperThreshold = upperThresh;
  }

  inline void setCannyThresholdsRatio(const float &lowerThreshRatio, const float &upperThreshRatio)
  {
    m_lowerThresholdRatio = lowerThreshRatio;
    m_upperThresholdRatio = upperThreshRatio;
  }

  inline void setGaussianFilterParameters(const int &kernelSize, const float &stdev)
  {
    m_gaussianKernelSize = kernelSize;
    m_gaussianStdev = stdev;
    initGaussianFilters();
  }

  inline void setGradientFilterAperture(const unsigned int &apertureSize)
  {
    m_gradientFilterKernelSize = apertureSize;
    initGradientFilters();
  }

  inline void setMask(const vpImage<bool> *p_mask)
  {
    mp_mask = p_mask;
  }

#if !defined(_WIN32) && (defined(__unix__) || defined(__unix) || (defined(__APPLE__) && defined(__MACH__))) // UNIX
  inline void setMinimumStackSize(const rlim_t &requiredStackSize)
  {
    m_minStackSize = requiredStackSize;
  }
#else
  inline void setMinimumStackSize(const unsigned int &requiredStackSize)
  {
    (void)requiredStackSize;
    static bool hasNotBeenDisplayed = true;
    if (hasNotBeenDisplayed) {
      std::cerr << "vpCannyEdgeDetection::setStackSize() has no effect on non-POSIX systems. The stack size is defined during compilation." << std::endl;
      hasNotBeenDisplayed = false;
    }
  }
#endif
 
  inline void setNbThread(const int &maxNbThread)
  {
#ifdef VISP_HAVE_OPENMP
    int nbThread = maxNbThread;
    if (nbThread < 0) {
      nbThread = omp_get_max_threads();
    }
    m_nbThread = nbThread;
#else
    (void)maxNbThread;
    m_nbThread = 1;
    std::cout << "[WARNING] OpenMP is not available, setting the number of threads is ignored." << std::endl;
#endif
  }

  inline void setStoreEdgePoints(const bool &storeEdgePoints)
  {
    m_storeListEdgePoints = storeEdgePoints;
  }



  inline const std::vector<vpImagePoint> &getEdgePointsList() const
  {
    if (!m_storeListEdgePoints) {
      throw(vpException(vpException::fatalError, "Asking for the edge-points list while not asking to store it"));
    }
    return m_edgePointsList;
  }

#if !defined(_WIN32) && (defined(__unix__) || defined(__unix) || (defined(__APPLE__) && defined(__MACH__))) // UNIX
  inline rlim_t getMinimumStackSize() const
  {
    return m_minStackSize;
  }
#else
  inline unsigned int getMinimumStackSize() const
  {
    const unsigned int limit = 65532000;
    return limit;
  }
#endif

  const vpImage<float> &getGIx() const
  {
    return m_dIx;
  }

  const vpImage<float> &getGIy() const
  {
    return m_dIy;
  }

  const vpImage<unsigned char> &getEdgeMap() const
  {
    return m_edgeMap;
  }

private:
  typedef enum EdgeType
  {
    STRONG_EDGE, 
    WEAK_EDGE,
    ON_CHECK, 
    NOT_EDGE 
  } EdgeType;
 
  // Filtering + gradient methods choice
  vpImageFilter::vpCannyFilteringAndGradientType m_filteringAndGradientType; 
 
  int m_nbThread; 
 
  // // Gaussian smoothing attributes
  int m_gaussianKernelSize; 
  float m_gaussianStdev;   
  vpArray2D<float> m_fg; 
 
  // // Gradient computation attributes
  bool m_areGradientAvailable; 
  unsigned int m_gradientFilterKernelSize; 
  vpArray2D<float> m_gradientFilterX; 
  vpArray2D<float> m_gradientFilterY; 
  vpImage<float> m_dIx; 
  vpImage<float> m_dIy; 
 
  // // Edge thining attributes
  std::vector<std::pair<unsigned int, float> > m_edgeCandidateAndGradient; 
 
  // // Hysteresis thresholding attributes
  float m_lowerThreshold; 
  float m_lowerThresholdRatio; 
  float m_upperThreshold; 
  float m_upperThresholdRatio; 
 
  // // Edge tracking attributes
#if !defined(_WIN32) && (defined(__unix__) || defined(__unix) || (defined(__APPLE__) && defined(__MACH__))) // UNIX
  rlim_t m_minStackSize; 
#endif
  bool m_storeListEdgePoints; 
  std::vector<unsigned int> m_activeEdgeCandidates; 
  vpImage<EdgeType> m_edgePointsCandidates; 
  vpImage<unsigned char> m_edgeMap; 
  std::vector<vpImagePoint> m_edgePointsList; 
  const vpImage<bool> *mp_mask; 
 
  float getGradientOrientation(const vpImage<float> &dIx, const vpImage<float> &dIy, const int &iter);
 
  void getInterpolWeightsAndOffsets(const float &gradientOrientation, float &alpha, float &beta, const int &nbCols,
                                    int &dRowGradAlpha, int &dRowGradBeta, int &dColGradAlpha, int &dColGradBeta);
 
  float getManhattanGradient(const vpImage<float> &dIx, const vpImage<float> &dIy, const int &iter);


  void initGaussianFilters();

  void initGradientFilters();

  void computeFilteringAndGradient(const vpImage<unsigned char> &I);

  void step3to5(const unsigned int &height, const unsigned int &width, const float &lowerThreshold, const float &upperThreshold);

  void performEdgeThinning(const float &lowerThreshold);

  void performHysteresisThresholding(const float &lowerThreshold, const float &upperThreshold);

  bool recursiveSearchForStrongEdge(const unsigned int &coordinates);

  void performEdgeTracking();
};
 
#ifdef VISP_HAVE_NLOHMANN_JSON
inline void from_json(const nlohmann::json &j, vpCannyEdgeDetection &detector)
{
  std::string filteringAndGradientName = vpImageFilter::vpCannyFiltAndGradTypeToStr(detector.m_filteringAndGradientType);
  filteringAndGradientName = j.value("filteringAndGradientType", filteringAndGradientName);
  detector.m_filteringAndGradientType = vpImageFilter::vpCannyFiltAndGradTypeFromStr(filteringAndGradientName);
  detector.m_gaussianKernelSize = j.value("gaussianSize", detector.m_gaussianKernelSize);
  detector.m_gaussianStdev = j.value("gaussianStdev", detector.m_gaussianStdev);
  detector.m_lowerThreshold = j.value("lowerThreshold", detector.m_lowerThreshold);
  detector.m_lowerThresholdRatio = j.value("lowerThresholdRatio", detector.m_lowerThresholdRatio);
  detector.m_gradientFilterKernelSize = j.value("gradientFilterKernelSize", detector.m_gradientFilterKernelSize);
  detector.m_upperThreshold = j.value("upperThreshold", detector.m_upperThreshold);
  detector.m_upperThresholdRatio = j.value("upperThresholdRatio", detector.m_upperThresholdRatio);
  detector.m_nbThread = j.value("nbThread", detector.m_nbThread);
  detector.reinit();
}
 
inline void to_json(nlohmann::json &j, const vpCannyEdgeDetection &detector)
{
  std::string filteringAndGradientName = vpImageFilter::vpCannyFiltAndGradTypeToStr(detector.m_filteringAndGradientType);
  j = nlohmann::json {
          {"filteringAndGradientType", filteringAndGradientName},
          {"gaussianSize", detector.m_gaussianKernelSize},
          {"gaussianStdev", detector.m_gaussianStdev},
          {"lowerThreshold", detector.m_lowerThreshold},
          {"lowerThresholdRatio", detector.m_lowerThresholdRatio},
          {"gradientFilterKernelSize", detector.m_gradientFilterKernelSize},
          {"upperThreshold", detector.m_upperThreshold},
          {"upperThresholdRatio", detector.m_upperThresholdRatio},
          {"nbThread", detector.m_nbThread}
  };
}
#endif
 
END_VISP_NAMESPACE
#endif