Point Cloud Library (PCL)  1.9.1-dev
sift_keypoint.h
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35 
36 #pragma once
37 
38 #include <pcl/keypoints/keypoint.h>
39 
40 namespace pcl
41 {
42  template<typename PointT>
44  {
45  inline float
46  operator () (const PointT & p) const
47  {
48  return p.intensity;
49  }
50  };
51  template<>
53  {
54  inline float
55  operator () (const PointNormal & p) const
56  {
57  return p.curvature;
58  }
59  };
60  template<>
62  {
63  inline float
64  operator () (const PointXYZRGB & p) const
65  {
66  return (static_cast<float> (299*p.r + 587*p.g + 114*p.b) / 1000.0f);
67  }
68  };
69  template<>
71  {
72  inline float
73  operator () (const PointXYZRGBA & p) const
74  {
75  return (static_cast<float> (299*p.r + 587*p.g + 114*p.b) / 1000.0f);
76  }
77  };
78 
79  /** \brief @b SIFTKeypoint detects the Scale Invariant Feature Transform
80  * keypoints for a given point cloud dataset containing points and intensity.
81  * This implementation adapts the original algorithm from images to point
82  * clouds.
83  *
84  * For more information about the image-based SIFT interest operator, see:
85  *
86  * David G. Lowe, "Distinctive image features from scale-invariant keypoints,"
87  * International Journal of Computer Vision, 60, 2 (2004), pp. 91-110.
88  *
89  * \author Michael Dixon
90  * \ingroup keypoints
91  */
92  template <typename PointInT, typename PointOutT>
93  class SIFTKeypoint : public Keypoint<PointInT, PointOutT>
94  {
95  public:
96  typedef boost::shared_ptr<SIFTKeypoint<PointInT, PointOutT> > Ptr;
97  typedef boost::shared_ptr<const SIFTKeypoint<PointInT, PointOutT> > ConstPtr;
98 
102 
109 
110  /** \brief Empty constructor. */
111  SIFTKeypoint () : min_scale_ (0.0), nr_octaves_ (0), nr_scales_per_octave_ (0),
112  min_contrast_ (-std::numeric_limits<float>::max ()), scale_idx_ (-1),
113  getFieldValue_ ()
114  {
115  name_ = "SIFTKeypoint";
116  }
117 
118  /** \brief Specify the range of scales over which to search for keypoints
119  * \param min_scale the standard deviation of the smallest scale in the scale space
120  * \param nr_octaves the number of octaves (i.e. doublings of scale) to compute
121  * \param nr_scales_per_octave the number of scales to compute within each octave
122  */
123  void
124  setScales (float min_scale, int nr_octaves, int nr_scales_per_octave);
125 
126  /** \brief Provide a threshold to limit detection of keypoints without sufficient contrast
127  * \param min_contrast the minimum contrast required for detection
128  */
129  void
130  setMinimumContrast (float min_contrast);
131 
132  protected:
133  bool
134  initCompute () override;
135 
136  /** \brief Detect the SIFT keypoints for a set of points given in setInputCloud () using the spatial locator in
137  * setSearchMethod ().
138  * \param output the resultant cloud of keypoints
139  */
140  void
141  detectKeypoints (PointCloudOut &output) override;
142 
143  private:
144  /** \brief Detect the SIFT keypoints for a given point cloud for a single octave.
145  * \param input the point cloud to detect keypoints in
146  * \param tree a k-D tree of the points in \a input
147  * \param base_scale the first (smallest) scale in the octave
148  * \param nr_scales_per_octave the number of scales to to compute
149  * \param output the resultant point cloud containing the SIFT keypoints
150  */
151  void
152  detectKeypointsForOctave (const PointCloudIn &input, KdTree &tree,
153  float base_scale, int nr_scales_per_octave,
154  PointCloudOut &output);
155 
156  /** \brief Compute the difference-of-Gaussian (DoG) scale space for the given input and scales
157  * \param input the point cloud for which the DoG scale space will be computed
158  * \param tree a k-D tree of the points in \a input
159  * \param scales a vector containing the scales over which to compute the DoG scale space
160  * \param diff_of_gauss the resultant DoG scale space (in a number-of-points by number-of-scales matrix)
161  */
162  void
163  computeScaleSpace (const PointCloudIn &input, KdTree &tree,
164  const std::vector<float> &scales,
165  Eigen::MatrixXf &diff_of_gauss);
166 
167  /** \brief Find the local minima and maxima in the provided difference-of-Gaussian (DoG) scale space
168  * \param input the input point cloud
169  * \param tree a k-D tree of the points in \a input
170  * \param diff_of_gauss the DoG scale space (in a number-of-points by number-of-scales matrix)
171  * \param extrema_indices the resultant vector containing the point indices of each keypoint
172  * \param extrema_scales the resultant vector containing the scale indices of each keypoint
173  */
174  void
175  findScaleSpaceExtrema (const PointCloudIn &input, KdTree &tree,
176  const Eigen::MatrixXf &diff_of_gauss,
177  std::vector<int> &extrema_indices, std::vector<int> &extrema_scales);
178 
179 
180  /** \brief The standard deviation of the smallest scale in the scale space.*/
181  float min_scale_;
182 
183  /** \brief The number of octaves (i.e. doublings of scale) over which to search for keypoints.*/
184  int nr_octaves_;
185 
186  /** \brief The number of scales to be computed for each octave.*/
187  int nr_scales_per_octave_;
188 
189  /** \brief The minimum contrast required for detection.*/
190  float min_contrast_;
191 
192  /** \brief Set to a value different than -1 if the output cloud has a "scale" field and we have to save
193  * the keypoints scales. */
194  int scale_idx_;
195 
196  /** \brief The list of fields present in the output point cloud data. */
197  std::vector<pcl::PCLPointField> out_fields_;
198 
200  };
201 }
202 
203 #include <pcl/keypoints/impl/sift_keypoint.hpp>
SIFTKeypoint detects the Scale Invariant Feature Transform keypoints for a given point cloud dataset ...
Definition: sift_keypoint.h:93
This file defines compatibility wrappers for low level I/O functions.
Definition: convolution.h:44
Keypoint< PointInT, PointOutT >::PointCloudOut PointCloudOut
boost::shared_ptr< SIFTKeypoint< PointInT, PointOutT > > Ptr
Definition: sift_keypoint.h:96
A point structure representing Euclidean xyz coordinates, and the RGBA color.
Keypoint represents the base class for key points.
Definition: keypoint.h:48
SIFTKeypoint()
Empty constructor.
Keypoint< PointInT, PointOutT >::KdTree KdTree
boost::shared_ptr< const SIFTKeypoint< PointInT, PointOutT > > ConstPtr
Definition: sift_keypoint.h:97
A point structure representing Euclidean xyz coordinates, together with normal coordinates and the su...
float operator()(const PointT &p) const
Definition: sift_keypoint.h:46
A point structure representing Euclidean xyz coordinates, and the RGB color.
Keypoint< PointInT, PointOutT >::PointCloudIn PointCloudIn
Definition: sift_keypoint.h:99