OpenCV/opencv_contrib/modules/line_descriptor/samples/knn_matching.cpp

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#include <iostream>
#include <opencv2/opencv_modules.hpp>

#ifdef HAVE_OPENCV_FEATURES2D

#include <opencv2/line_descriptor.hpp>
#include <opencv2/core/utility.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/features2d.hpp>
#include <opencv2/highgui.hpp>

#include <vector>
#include <time.h>

using namespace cv;
using namespace cv::line_descriptor;

static const char* keys =
{ "{@image_path1 | | Image path 1 }"
    "{@image_path2 | | Image path 2 }" };

static void help()
{
  std::cout << "\nThis example shows the functionalities of descriptors matching\n" << "Please, run this sample using a command in the form\n"
            << "./example_line_descriptor_matching <path_to_input_image 1>" << "<path_to_input_image 2>" << std::endl;

}

uchar invertSingleBits( uchar dividend_char, int numBits );

/* invert numBits bits in input char */
uchar invertSingleBits( uchar dividend_char, int numBits )
{
  std::vector<int> bin_vector;
  long dividend;
  long bin_num;

  /* convert input char to a long */
  dividend = (long) dividend_char;

  /*if a 0 has been obtained, just generate a 8-bit long vector of zeros */
  if( dividend == 0 )
    bin_vector = std::vector<int>( 8, 0 );

  /* else, apply classic decimal to binary conversion */
  else
  {
    while ( dividend >= 1 )
    {
      bin_num = dividend % 2;
      dividend /= 2;
      bin_vector.push_back( bin_num );
    }
  }

  /* ensure that binary vector always has length 8 */
  if( bin_vector.size() < 8 )
  {
    std::vector<int> zeros( 8 - bin_vector.size(), 0 );
    bin_vector.insert( bin_vector.end(), zeros.begin(), zeros.end() );
  }

  /* invert numBits bits */
  for ( int index = 0; index < numBits; index++ )
  {
    if( bin_vector[index] == 0 )
      bin_vector[index] = 1;

    else
      bin_vector[index] = 0;
  }

  /* reconvert to decimal */
  uchar result = 0;
  for ( int i = (int) bin_vector.size() - 1; i >= 0; i-- )
    result += (uchar) ( bin_vector[i] * (1 << i) );

  return result;
}

int main( int argc, char** argv )
{
  /* get parameters from comand line */
  CommandLineParser parser( argc, argv, keys );
  String image_path1 = parser.get<String>( 0 );
  String image_path2 = parser.get<String>( 1 );

  if( image_path1.empty() || image_path2.empty() )
  {
    help();
    return -1;
  }

  /* load image */
  cv::Mat imageMat1 = imread( image_path1, 1 );
  cv::Mat imageMat2 = imread( image_path2, 1 );

  if( imageMat1.data == NULL || imageMat2.data == NULL )
  {
    std::cout << "Error, images could not be loaded. Please, check their paths" << std::endl;
  }

  /* create binary masks */
  cv::Mat mask1 = Mat::ones( imageMat1.size(), CV_8UC1 );
  cv::Mat mask2 = Mat::ones( imageMat2.size(), CV_8UC1 );

  /* create a pointer to a BinaryDescriptor object with default parameters */
  Ptr<BinaryDescriptor> bd = BinaryDescriptor::createBinaryDescriptor();

  /* compute lines */
  std::vector<KeyLine> keylines1, keylines2;
  bd->detect( imageMat1, keylines1, mask1 );
  bd->detect( imageMat2, keylines2, mask2 );

  /* compute descriptors */
  cv::Mat descr1, descr2;
  bd->compute( imageMat1, keylines1, descr1 );
  bd->compute( imageMat2, keylines2, descr2 );

  /* create a BinaryDescriptorMatcher object */
  Ptr<BinaryDescriptorMatcher> bdm = BinaryDescriptorMatcher::createBinaryDescriptorMatcher();

  /* make a copy of descr2 mat */
  Mat descr2Copy = descr1.clone();

  /* randomly change some bits in original descriptors */
  srand( (unsigned int) time( NULL ) );

  for ( int j = 0; j < descr1.rows; j++ )
  {
    /* select a random column */
    int randCol = rand() % 32;

    /* get correspondent data */
    uchar u = descr1.at<uchar>( j, randCol );

    /* change bits */
    for ( int k = 1; k <= 5; k++ )
    {
      /* copy current row to train matrix */
      descr2Copy.push_back( descr1.row( j ) );

      /* invert k bits */
      uchar uc = invertSingleBits( u, k );

      /* update current row in train matrix */
      descr2Copy.at<uchar>( descr2Copy.rows - 1, randCol ) = uc;
    }
  }

  /* prepare a structure to host matches */
  std::vector<std::vector<DMatch> > matches;

  /* require knn match */
  bdm->knnMatch( descr1, descr2, matches, 6 );

}

#else

int main()
{
    std::cerr << "OpenCV was built without features2d module" << std::endl;
    return 0;
}

#endif // HAVE_OPENCV_FEATURES2D