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descriptor_pairing.h
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1 /* +---------------------------------------------------------------------------+
2  | Mobile Robot Programming Toolkit (MRPT) |
3  | http://www.mrpt.org/ |
4  | |
5  | Copyright (c) 2005-2017, Individual contributors, see AUTHORS file |
6  | See: http://www.mrpt.org/Authors - All rights reserved. |
7  | Released under BSD License. See details in http://www.mrpt.org/License |
8  +---------------------------------------------------------------------------+ */
9 
10 #ifndef mrpt_vision_descriptor_pairing_H
11 #define mrpt_vision_descriptor_pairing_H
12 
13 #include <mrpt/vision/types.h>
14 
15 namespace mrpt
16 {
17  namespace vision
18  {
19  /** \addtogroup mrptvision_features
20  @{ */
21 
22  /** Search for pairings between two sets of visual descriptors (for now, only SURF
23  * and SIFT features are considered).
24  * Pairings are returned in one of two formats (or both of them simultaneously),
25  * depending on the non-NULL output containers present in the call.
26  *
27  * \code
28  * CFeatureList feats1, feats2;
29  * // Populate feature lists [...]
30  *
31  * // Create kd-tree for SIFT features of "feats2":
32  * TSIFTDescriptorsKDTreeIndex<double> feats2_kdtree(feats2);
33  *
34  * // Search correspondences:
35  * std::vector<vector_size_t> pairings_1_to_multi_2;
36  * std::vector<std::pair<size_t,size_t> > pairings_1_to_2;
37  * mrpt::vision::find_descriptor_pairings(
38  * &pairings_1_to_multi_2, // Can be set to NULL if not needed
39  * &pairings_1_to_2, // Can be set to NULL if not needed
40  * feats1, feats2_kdtree, // The two sets of features
41  * mrpt::vision::descSIFT // Select descriptor to use
42  * // [further optional params]
43  * );
44  * \endcode
45  *
46  * \sa TSIFTDescriptorsKDTreeIndex, TSURFDescriptorsKDTreeIndex
47  */
48  template <class DESCRIPTOR_KDTREE>
50  std::vector<vector_size_t> * pairings_1_to_multi_2,
51  std::vector<std::pair<size_t,size_t> > * pairings_1_to_2,
52  const CFeatureList & feats_img1,
53  const DESCRIPTOR_KDTREE & feats_img2_kdtree,
54  const mrpt::vision::TDescriptorType descriptor = descSIFT,
55  const size_t max_neighbors = 4,
56  const double max_relative_distance = 1.2,
57  const typename DESCRIPTOR_KDTREE::kdtree_t::DistanceType max_distance = std::numeric_limits<typename DESCRIPTOR_KDTREE::kdtree_t::DistanceType>::max()
58  )
59  {
61  ASSERT_ABOVEEQ_(max_neighbors,1)
62  ASSERT_(pairings_1_to_multi_2!=NULL || pairings_1_to_2!=NULL)
63 
64  typedef typename DESCRIPTOR_KDTREE::kdtree_t::ElementType KDTreeElementType; // The expected data type of elements for the kd-tree
65  typedef typename DESCRIPTOR_KDTREE::kdtree_t::DistanceType KDTreeDistanceType;
66 
67  const size_t N=feats_img1.size();
68  if (pairings_1_to_multi_2) pairings_1_to_multi_2->assign(N, vector_size_t()); // Reset output container
69  if (pairings_1_to_2) { pairings_1_to_2->clear(); pairings_1_to_2->reserve(N); }
70 
71  size_t overall_pairs = 0;
72 
73  if (!N) return overall_pairs; // No features -> nothing to do
74 
75  if (descriptor==descSIFT) {
76  ASSERTMSG_(feats_img1[0]->descriptors.hasDescriptorSIFT(), "Request to match SIFT features but feats_img1 has no SIFT descriptors!")
77  ASSERTMSG_(sizeof(KDTreeElementType)==sizeof(feats_img1[0]->descriptors.SIFT[0]),"Incorrect data type kd_tree::ElementType for SIFT (should be uint8_t)")
78  }
79  else if (descriptor==descSURF) {
80  ASSERTMSG_(feats_img1[0]->descriptors.hasDescriptorSURF(), "Request to match SURF features but feats_img1 has no SURF descriptors!")
81  ASSERTMSG_(sizeof(KDTreeElementType)==sizeof(feats_img1[0]->descriptors.SURF[0]),"Incorrect data type kd_tree::ElementType for SURF (should be float)")
82  }
83  else { THROW_EXCEPTION("This function only supports SIFT or SURFT descriptors") }
84 
85  std::vector<size_t> indices(max_neighbors);
86  std::vector<double> distances(max_neighbors);
87 
88  for (size_t i=0;i<N;i++)
89  {
90  const CFeature::TDescriptors &descs = feats_img1[i]->descriptors;
91 
92  const void * ptr_query;
93  if (descriptor==descSIFT) ptr_query = &descs.SIFT[0];
94  else if (descriptor==descSURF) ptr_query = &descs.SURF[0];
95 
96  feats_img2_kdtree.get_kdtree().knnSearch(
97  static_cast<const KDTreeElementType*>( ptr_query ), // Query point
98  max_neighbors, // Number of neigbors
99  &indices[0], &distances[0] // Output
100  );
101 
102  // Include all correspondences below the absolute and the relative threshold (indices comes ordered by distances):
103  const KDTreeDistanceType this_thresh = std::min( max_relative_distance*distances[0], max_distance);
104  for (size_t j=0;j<max_neighbors;j++)
105  {
106  if (distances[j]<=this_thresh) {
107  overall_pairs++;
108  if (pairings_1_to_multi_2) (*pairings_1_to_multi_2)[i].push_back(indices[j]);
109  if (pairings_1_to_2) pairings_1_to_2->push_back(std::make_pair(i,indices[j]));
110  }
111  else break;
112  }
113  }
114  return overall_pairs;
115  MRPT_END
116  }
117 
118  /** @} */
119 
120  }
121 }
122 #endif
123 
size_t find_descriptor_pairings(std::vector< vector_size_t > *pairings_1_to_multi_2, std::vector< std::pair< size_t, size_t > > *pairings_1_to_2, const CFeatureList &feats_img1, const DESCRIPTOR_KDTREE &feats_img2_kdtree, const mrpt::vision::TDescriptorType descriptor=descSIFT, const size_t max_neighbors=4, const double max_relative_distance=1.2, const typename DESCRIPTOR_KDTREE::kdtree_t::DistanceType max_distance=std::numeric_limits< typename DESCRIPTOR_KDTREE::kdtree_t::DistanceType >::max())
Search for pairings between two sets of visual descriptors (for now, only SURF and SIFT features are ...
#define min(a, b)
GLuint GLuint GLsizei GLenum const GLvoid * indices
Definition: glew.h:1167
size_t size() const
Definition: CFeature.h:280
#define THROW_EXCEPTION(msg)
std::vector< float > SURF
SURF feature descriptor.
Definition: CFeature.h:89
#define MRPT_END
std::vector< uint8_t > SIFT
SIFT feature descriptor.
Definition: CFeature.h:88
All the possible descriptors this feature may have.
Definition: CFeature.h:84
A list of visual features, to be used as output by detectors, as input/output by trackers, etc.
Definition: CFeature.h:211
TDescriptorType
The bitwise OR combination of values of TDescriptorType are used in CFeatureExtraction::computeDescri...
#define MRPT_START
#define ASSERT_ABOVEEQ_(__A, __B)
#define ASSERT_(f)
std::vector< size_t > vector_size_t
Definition: types_simple.h:25
#define ASSERTMSG_(f, __ERROR_MSG)



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