composants connectés en OpenCV

à partir de la version 3.0, OpenCV a connectedComponents fonction.

regardez cvFindContours fonction. Il est très polyvalent - il peut trouver à la fois les contours intérieurs et extérieurs, et retourner les résultats dans une variété de formats (par exemple Liste Plate vs structure de l'arbre). Une fois que vous avez les contours, les fonctions comme cvContourArea permet de déterminer les propriétés de base du composant connecté correspondant à un contour particulier.

Si vous préférez utiliser la nouvelle interface C++ (par opposition à l'ancienne C-style interface I décrit ci-dessus), puis les noms de fonction sont similaires.

set-std=C++0x option lors de la compilation

.h fichier

//connected_components.h
#ifndef CONNECTED_COMPONENTS_H_
#define CONNECTED_COMPONENTS_H_
#include <opencv2/core/core.hpp>
#include <memory>

class DisjointSet {
  private:
    std::vector<int> m_disjoint_array;
    int m_subset_num;
  public:
    DisjointSet();
    DisjointSet(int size);
    ~DisjointSet();
    int add(); //add a new element, which is a subset by itself;
    int find(int x); //return the root of x
    void unite(int x, int y);
    int getSubsetNum(void);
};

class ConnectedComponent {
private:
  cv::Rect m_bb;
  int m_pixel_count;
  std::shared_ptr< std::vector<cv::Point2i> > m_pixels;
public:
  ConnectedComponent();
  ConnectedComponent(int x, int y);
  ~ConnectedComponent();
  void addPixel(int x, int y);
  int getBoundingBoxArea(void) const;
  cv::Rect getBoundingBox(void) const;
  int getPixelCount(void) const;
  std::shared_ptr< const std::vector<cv::Point2i> > getPixels(void) const;
};

void findCC(const cv::Mat& src, std::vector<ConnectedComponent>& cc);
#endif //CONNECTED_COMPONENTS_H_

.cc fichier

//connected_components.cpp
#include "connected_components.h"

using namespace std;
/** DisjointSet **/
DisjointSet::DisjointSet() :
  m_disjoint_array(),
  m_subset_num(0)
{  }

DisjointSet::DisjointSet(int size) :
  m_disjoint_array(),
  m_subset_num(0)
{
  m_disjoint_array.reserve(size);
}

DisjointSet::~DisjointSet()
{  }

//add a new element, which is a subset by itself;
int DisjointSet::add()
{
  int cur_size = m_disjoint_array.size();
  m_disjoint_array.push_back(cur_size);
  m_subset_num ++;
  return cur_size;
}
//return the root of x
int DisjointSet::find(int x)
{
  if (m_disjoint_array[x] < 0 || m_disjoint_array[x] == x)
    return x;
  else {
    m_disjoint_array[x] = this->find(m_disjoint_array[x]);
    return m_disjoint_array[x];
  }
}
// point the x and y to smaller root of the two
void DisjointSet::unite(int x, int y)
{
  if (x==y) {
    return;
  }
  int xRoot = find(x);
  int yRoot = find(y);
  if (xRoot == yRoot)
    return;
  else if (xRoot < yRoot) {
    m_disjoint_array[yRoot] = xRoot;
  }
  else {
    m_disjoint_array[xRoot] = yRoot;
  }
  m_subset_num--;
}

int DisjointSet::getSubsetNum()
{
  return m_subset_num;
}

/** ConnectedComponent **/
ConnectedComponent::ConnectedComponent() :
  m_bb(0,0,0,0),
  m_pixel_count(0),
  m_pixels()
{
  m_pixels = std::make_shared< std::vector<cv::Point2i> > ();
}

ConnectedComponent::ConnectedComponent(int x, int y) :
  m_bb(x,y,1,1),
  m_pixel_count(1),
  m_pixels()
{
  m_pixels = std::make_shared< std::vector<cv::Point2i> > ();
}

ConnectedComponent::~ConnectedComponent(void)
{ }

void ConnectedComponent::addPixel(int x, int y) {
  m_pixel_count++;
  // new bounding box;
  if (m_pixel_count == 0) {
    m_bb = cv::Rect(x,y,1,1);
  }
  // extend bounding box if necessary
  else {
    if (x < m_bb.x ) {
      m_bb.width+=(m_bb.x-x);
      m_bb.x = x;
    }
    else if ( x > (m_bb.x+m_bb.width) ) {
      m_bb.width=(x-m_bb.x);
    }
    if (y < m_bb.y ) {
      m_bb.height+=(m_bb.y-y);
      m_bb.y = y;
    }
    else if ( y > (m_bb.y+m_bb.height) ) {
      m_bb.height=(y-m_bb.y);
    }
  }
  m_pixels->push_back(cv::Point(x,y));
}

int ConnectedComponent::getBoundingBoxArea(void) const {
  return (m_bb.width*m_bb.height);
}

cv::Rect ConnectedComponent::getBoundingBox(void) const {
  return m_bb;
}

std::shared_ptr< const std::vector<cv::Point2i> > ConnectedComponent::getPixels(void) const {
  return m_pixels;
}


int ConnectedComponent::getPixelCount(void) const {
  return m_pixel_count;
}

/** find connected components **/

void findCC(const cv::Mat& src, std::vector<ConnectedComponent>& cc) {
  if (src.empty()) return;
  CV_Assert(src.type() == CV_8U);
  cc.clear();
  int total_pix = src.total();
  int frame_label[total_pix];
  DisjointSet labels(total_pix);
  int root_map[total_pix];
  int x, y;
  const uchar* cur_p;
  const uchar* prev_p = src.ptr<uchar>(0);
  int left_val, up_val;
  int cur_idx, left_idx, up_idx;
  cur_idx = 0;
  //first logic loop
  for (y = 0; y < src.rows; y++ ) {
    cur_p = src.ptr<uchar>(y);
    for (x = 0; x < src.cols; x++, cur_idx++) {
      left_idx = cur_idx - 1;
      up_idx = cur_idx - src.size().width;
      if ( x == 0)
        left_val = 0;
      else
        left_val = cur_p[x-1];
      if (y == 0)
        up_val = 0;
      else
        up_val = prev_p[x];
      if (cur_p[x] > 0) {
        //current pixel is foreground and has no connected neighbors
        if (left_val == 0 && up_val == 0) {
          frame_label[cur_idx] = (int)labels.add();
          root_map[frame_label[cur_idx]] = -1;
        }
        //current pixel is foreground and has left neighbor connected
        else if (left_val != 0 && up_val == 0) {
          frame_label[cur_idx] = frame_label[left_idx];
        }
        //current pixel is foreground and has up neighbor connect
        else if (up_val != 0 && left_val == 0) {
          frame_label[cur_idx] = frame_label[up_idx];
        }
        //current pixel is foreground and is connected to left and up neighbors
        else {
          frame_label[cur_idx] = (frame_label[left_idx] > frame_label[up_idx]) ? frame_label[up_idx] : frame_label[left_idx];
          labels.unite(frame_label[left_idx], frame_label[up_idx]);
        }
      }//endif
      else {
        frame_label[cur_idx] = -1;
      }
    } //end for x
    prev_p = cur_p;
  }//end for y
  //second loop logic
  cur_idx = 0;
  int curLabel;
  int connCompIdx = 0;
  for (y = 0; y < src.size().height; y++ ) {
    for (x = 0; x < src.size().width; x++, cur_idx++) {
      curLabel = frame_label[cur_idx];
      if (curLabel != -1) {
        curLabel = labels.find(curLabel);
        if( root_map[curLabel] != -1 ) {
          cc[root_map[curLabel]].addPixel(x, y);
        }
        else {
          cc.push_back(ConnectedComponent(x,y));
          root_map[curLabel] = connCompIdx;
          connCompIdx++;
        }
      }
    }//end for x
  }//end for y
}

si cela ne vous dérange pas d'utiliser une bibliothèque externe qui utilise OpenCV, vous pouvez le faire en utilisant cvBlobsLib.

une bibliothèque pour effectuer des images binaires connected component labelling ( similaire à la fonction Matlab de regionprops). Il fournit également des fonctions pour manipuler, filtrer et extraire les résultats des blobs extraits, voir la section Caractéristiques pour plus d'information.

suivant le code de DXM ci-dessus qui suppose 4 composants connectés, voici une version pour 'findCC' qui détecte 8 composants connectés.

void findCC(const cv::Mat& src, std::vector<ConnectedComponent>& cc) {
if (src.empty()) return;
CV_Assert(src.type() == CV_8U);
cc.clear();
int total_pix = int(src.total());
int *frame_label = new int[total_pix];
DisjointSet labels(total_pix);
int *root_map = new int[total_pix];
int x, y;
const uchar* cur_p;
const uchar* prev_p = src.ptr<uchar>(0);
int left_val, up_val, up_left_val, up_right_val;
int cur_idx, left_idx, up_idx, up_left_idx, up_right_idx;
cur_idx = 0;
//first logic loop
for (y = 0; y < src.rows; y++) {
    cur_p = src.ptr<uchar>(y);
    for (x = 0; x < src.cols; x++, cur_idx++) {
        left_idx = cur_idx - 1;
        up_idx = cur_idx - src.size().width;
        up_left_idx = up_idx - 1;
        up_right_idx = up_idx + 1;

        if (x == 0)
        {
            left_val = 0;
        }
        else
        {
            left_val = cur_p[x - 1];
        }
        if (y == 0)
        {
            up_val = 0;
        }
        else
        {
            up_val = prev_p[x];
        }
        if (x == 0 || y == 0)
        {
            up_left_val = 0;
        }
        else
        {
            up_left_val = prev_p[x-1];
        }
        if (x == src.cols - 1 || y == 0)
        {
            up_right_val = 0;
        }
        else
        {
            up_right_val = prev_p[x+1];
        }

        if (cur_p[x] > 0) {
            //current pixel is foreground and has no connected neighbors
            if (left_val == 0 && up_val == 0 && up_left_val == 0 && up_right_val == 0) {
                frame_label[cur_idx] = (int)labels.add();
                root_map[frame_label[cur_idx]] = -1;
            }

            //Current pixel is foreground and has at least one neighbor
            else
            {
                vector<int> frame_lbl;
                frame_lbl.reserve(4);
                //Find minimal label
                int min_frame_lbl = INT_MAX;
                int valid_entries_num = 0;

                if (left_val != 0)
                {
                    frame_lbl.push_back(frame_label[left_idx]);
                    min_frame_lbl = min(min_frame_lbl, frame_label[left_idx]);
                    valid_entries_num++;
                }
                if (up_val != 0)
                {
                    frame_lbl.push_back(frame_label[up_idx]);
                    min_frame_lbl = min(min_frame_lbl, frame_label[up_idx]);
                    valid_entries_num++;
                }
                if (up_left_val != 0)
                {
                    frame_lbl.push_back(frame_label[up_left_idx]);
                    min_frame_lbl = min(min_frame_lbl, frame_label[up_left_idx]);
                    valid_entries_num++;
                }
                if (up_right_val != 0)
                {
                    frame_lbl.push_back(frame_label[up_right_idx]);
                    min_frame_lbl = min(min_frame_lbl, frame_label[up_right_idx]);
                    valid_entries_num++;
                }

                CV_Assert(valid_entries_num > 0);
                frame_label[cur_idx] = min_frame_lbl;

                //Unite if necessary
                if (valid_entries_num > 1)
                {
                    for (size_t i = 0; i < frame_lbl.size(); i++)
                    {
                        labels.unite(frame_lbl[i], min_frame_lbl);
                    }
                }
            }

        }//endif
        else {
            frame_label[cur_idx] = -1;
        }
    } //end for x
    prev_p = cur_p;
}//end for y
//second loop logic
cur_idx = 0;
int curLabel;
int connCompIdx = 0;
for (y = 0; y < src.size().height; y++) {
    for (x = 0; x < src.size().width; x++, cur_idx++) {
        curLabel = frame_label[cur_idx];
        if (curLabel != -1) {
            curLabel = labels.find(curLabel);
            if (root_map[curLabel] != -1) {
                cc[root_map[curLabel]].addPixel(x, y);
            }
            else {
                cc.push_back(ConnectedComponent(x, y));
                root_map[curLabel] = connCompIdx;
                connCompIdx++;
            }
        }
    }//end for x
}//end for y

//Free up allocated memory
delete[] frame_label;
delete[] root_map;

}