LSDDetector.cpp

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#include "precomp.hpp"

//using namespace cv;
namespace cv
{
namespace line_descriptor
{
Ptr<LSDDetector> LSDDetector::createLSDDetector()
{
  return Ptr<LSDDetector>( new LSDDetector() );
}

/* compute Gaussian pyramid of input image */
void LSDDetector::computeGaussianPyramid( const Mat& image, int numOctaves, int scale )
{
  /* clear class fields */
  gaussianPyrs.clear();

  /* insert input image into pyramid */
  cv::Mat currentMat = image.clone();
  //cv::GaussianBlur( currentMat, currentMat, cv::Size( 5, 5 ), 1 );
  gaussianPyrs.push_back( currentMat );

  /* fill Gaussian pyramid */
  for ( int pyrCounter = 1; pyrCounter < numOctaves; pyrCounter++ )
  {
    /* compute and store next image in pyramid and its size */
    pyrDown( currentMat, currentMat, Size( currentMat.cols / scale, currentMat.rows / scale ) );
    gaussianPyrs.push_back( currentMat );
  }
}

/* check lines' extremes */
inline void checkLineExtremes( cv::Vec4f& extremes, cv::Size imageSize )
{

  if( extremes[0] < 0 )
    extremes[0] = 0;

  if( extremes[0] >= imageSize.width )
    extremes[0] = (float)imageSize.width - 1.0f;

  if( extremes[2] < 0 )
    extremes[2] = 0;

  if( extremes[2] >= imageSize.width )
    extremes[2] = (float)imageSize.width - 1.0f;

  if( extremes[1] < 0 )
    extremes[1] = 0;

  if( extremes[1] >= imageSize.height )
    extremes[1] = (float)imageSize.height - 1.0f;

  if( extremes[3] < 0 )
    extremes[3] = 0;

  if( extremes[3] >= imageSize.height )
    extremes[3] = (float)imageSize.height - 1.0f;
}

/* requires line detection (only one image) */
void LSDDetector::detect( const Mat& image, CV_OUT std::vector<KeyLine>& keylines, int scale, int numOctaves, const Mat& mask )
{
  if( mask.data != NULL && ( mask.size() != image.size() || mask.type() != CV_8UC1 ) )
    CV_Error( Error::StsBadArg, "Mask error while detecting lines: please check its dimensions and that data type is CV_8UC1" );

  else
    detectImpl( image, keylines, numOctaves, scale, mask );
}

/* requires line detection (more than one image) */
void LSDDetector::detect( const std::vector<Mat>& images, std::vector<std::vector<KeyLine> >& keylines, int scale, int numOctaves,
                          const std::vector<Mat>& masks ) const
{
  /* detect lines from each image */
  for ( size_t counter = 0; counter < images.size(); counter++ )
  {
    if( masks[counter].data != NULL && ( masks[counter].size() != images[counter].size() || masks[counter].type() != CV_8UC1 ) )
      CV_Error( Error::StsBadArg, "Masks error while detecting lines: please check their dimensions and that data types are CV_8UC1" );

    else
      detectImpl( images[counter], keylines[counter], numOctaves, scale, masks[counter] );
  }
}

/* implementation of line detection */
void LSDDetector::detectImpl( const Mat& imageSrc, std::vector<KeyLine>& keylines, int numOctaves, int scale, const Mat& mask ) const
{
  cv::Mat image;
  if( imageSrc.channels() != 1 )
    cvtColor( imageSrc, image, COLOR_BGR2GRAY );
  else
    image = imageSrc.clone();

  /*check whether image depth is different from 0 */
  if( image.depth() != 0 )
    CV_Error( Error::BadDepth, "Error, depth image!= 0" );

  /* create a pointer to self */
  LSDDetector *lsd = const_cast<LSDDetector*>( this );

  /* compute Gaussian pyramids */
  lsd->computeGaussianPyramid( image, numOctaves, scale );

  /* create an LSD extractor */
  cv::Ptr<cv::LineSegmentDetector> ls = cv::createLineSegmentDetector( cv::LSD_REFINE_ADV );

  /* prepare a vector to host extracted segments */
  std::vector<std::vector<cv::Vec4f> > lines_lsd;

  /* extract lines */
  for ( int i = 0; i < numOctaves; i++ )
  {
    std::vector<Vec4f> octave_lines;
    ls->detect( gaussianPyrs[i], octave_lines );
    lines_lsd.push_back( octave_lines );
  }

  /* create keylines */
  int class_counter = -1;
  for ( int octaveIdx = 0; octaveIdx < (int) lines_lsd.size(); octaveIdx++ )
  {
    float octaveScale = pow( (float)scale, octaveIdx );
    for ( int k = 0; k < (int) lines_lsd[octaveIdx].size(); k++ )
    {
      KeyLine kl;
      cv::Vec4f extremes = lines_lsd[octaveIdx][k];

      /* check data validity */
      checkLineExtremes( extremes, gaussianPyrs[octaveIdx].size() );

      /* fill KeyLine's fields */
      kl.startPointX = extremes[0] * octaveScale;
      kl.startPointY = extremes[1] * octaveScale;
      kl.endPointX = extremes[2] * octaveScale;
      kl.endPointY = extremes[3] * octaveScale;
      kl.sPointInOctaveX = extremes[0];
      kl.sPointInOctaveY = extremes[1];
      kl.ePointInOctaveX = extremes[2];
      kl.ePointInOctaveY = extremes[3];
      kl.lineLength = (float) sqrt( pow( extremes[0] - extremes[2], 2 ) + pow( extremes[1] - extremes[3], 2 ) );

      /* compute number of pixels covered by line */
      LineIterator li( gaussianPyrs[octaveIdx], Point2f( extremes[0], extremes[1] ), Point2f( extremes[2], extremes[3] ) );
      kl.numOfPixels = li.count;

      kl.angle = atan2( ( kl.endPointY - kl.startPointY ), ( kl.endPointX - kl.startPointX ) );
      kl.class_id = ++class_counter;
      kl.octave = octaveIdx;
      kl.size = ( kl.endPointX - kl.startPointX ) * ( kl.endPointY - kl.startPointY );
      kl.response = kl.lineLength / max( gaussianPyrs[octaveIdx].cols, gaussianPyrs[octaveIdx].rows );
      kl.pt = Point2f( ( kl.endPointX + kl.startPointX ) / 2, ( kl.endPointY + kl.startPointY ) / 2 );

      keylines.push_back( kl );
    }
  }

  /* delete undesired KeyLines, according to input mask */
  if( !mask.empty() )
  {
    for ( size_t keyCounter = 0; keyCounter < keylines.size(); keyCounter++ )
    {
      KeyLine kl = keylines[keyCounter];
      if( mask.at<uchar>( (int) kl.startPointY, (int) kl.startPointX ) == 0 && mask.at<uchar>( (int) kl.endPointY, (int) kl.endPointX ) == 0 )
      {
        keylines.erase( keylines.begin() + keyCounter );
        keyCounter--;
      }
    }
  }

}
}
}