# cv::SparseMat Class Reference

`#include <core.hpp>`

Inheritance diagram for cv::SparseMat:

List of all members.

## Classes

struct | Hdr
| the sparse matrix header More...
struct | Node
| sparse matrix node - element of a hash table More...

## Public Types

enum | { MAGIC_VAL = 0x42FD0000, MAX_DIM = CV_MAX_DIM, HASH_SCALE = 0x5bd1e995, HASH_BIT = 0x80000000 }
typedef SparseMatConstIterator | const_iterator
typedef SparseMatIterator | iterator

## Public Member Functions

void | addref ()
| manually increments the reference counter to the header.
void | assignTo (SparseMat &m, int type=-1) const
int | channels () const
| returns the number of channels
void | clear ()
| sets all the sparse matrix elements to 0, which means clearing the hash table.
SparseMat | clone () const
| creates full copy of the matrix
void | convertTo (Mat &m, int rtype, double alpha=1, double beta=0) const
| converts sparse matrix to dense n-dim matrix with optional type conversion and scaling.
void | convertTo (SparseMat &m, int rtype, double alpha=1) const
| multiplies all the matrix elements by the specified scale factor alpha and converts the results to the specified data type
void | copyTo (SparseMat &m) const
| copies all the data to the destination matrix. All the previous content of m is erased
void | copyTo (Mat &m) const
| converts sparse matrix to dense matrix.
void | create (int dims, const int *_sizes, int _type)
| reallocates sparse matrix.
int | depth () const
| returns the depth of sparse matrix elements
int | dims () const
| returns the matrix dimensionality
size_t | elemSize () const
| returns the size of each element in bytes (not including the overhead - the space occupied by SparseMat::Node elements)
size_t | elemSize1 () const
| returns elemSize()/channels()
SparseMatIterator | end ()
| returns the sparse matrix iterator at the matrix end
SparseMatConstIterator | end () const
| returns the read-only sparse matrix iterator at the matrix end
template<typename _Tp >
SparseMatIterator_< _Tp > | end ()
| returns the typed sparse matrix iterator at the matrix end
template<typename _Tp >
SparseMatConstIterator_< _Tp > | end () const
| returns the typed read-only sparse matrix iterator at the matrix end
size_t | hash (const int *idx) const
| computes the element hash value (nD case)
size_t | hash (int i0) const
| computes the element hash value (1D case)
size_t | hash (int i0, int i1) const
| computes the element hash value (2D case)
size_t | hash (int i0, int i1, int i2) const
| computes the element hash value (3D case)
uchar * | newNode (const int *idx, size_t hashval)
Node * | node (size_t nidx)
const Node * | node (size_t nidx) const
size_t | nzcount () const
| returns the number of non-zero elements (=the number of hash table nodes)
| operator CvSparseMat * () const
| converts sparse matrix to the old-style representation; all the elements are copied.
SparseMat & | operator= (const Mat &m)
| equivalent to the corresponding constructor
SparseMat & | operator= (const SparseMat &m)
| assignment operator. This is O(1) operation, i.e. no data is copied
void | release ()
void | removeNode (size_t hidx, size_t nidx, size_t previdx)
void | resizeHashTab (size_t newsize)
int | size (int i) const
| returns the size of i-th matrix dimension (or 0)
const int * | size () const
| returns the array of sizes, or NULL if the matrix is not allocated
| SparseMat ()
| default constructor
| SparseMat (const CvSparseMat *m)
| converts old-style sparse matrix to the new-style. All the data is copied
| SparseMat (const Mat &m)
| converts dense 2d matrix to the sparse form
| SparseMat (const SparseMat &m)
| copy constructor
| SparseMat (int dims, const int *_sizes, int _type)
| creates matrix of the specified size and type
int | type () const
| returns type of sparse matrix elements
template<typename _Tp >
const _Tp & | value (const Node *n) const
| returns the value stored in the sparse martix node
template<typename _Tp >
_Tp & | value (Node *n)
| returns the value stored in the sparse martix node
| ~SparseMat ()
| the destructor
uchar * | ptr (int i0, bool createMissing, size_t *hashval=0)
| returns pointer to the specified element (1D case)
uchar * | ptr (int i0, int i1, bool createMissing, size_t *hashval=0)
| returns pointer to the specified element (2D case)
uchar * | ptr (int i0, int i1, int i2, bool createMissing, size_t *hashval=0)
| returns pointer to the specified element (3D case)
uchar * | ptr (const int *idx, bool createMissing, size_t *hashval=0)
| returns pointer to the specified element (nD case)
template<typename _Tp >
_Tp & | ref (int i0, size_t *hashval=0)
| returns reference to the specified element (1D case)
template<typename _Tp >
_Tp & | ref (int i0, int i1, size_t *hashval=0)
| returns reference to the specified element (2D case)
template<typename _Tp >
_Tp & | ref (int i0, int i1, int i2, size_t *hashval=0)
| returns reference to the specified element (3D case)
template<typename _Tp >
_Tp & | ref (const int *idx, size_t *hashval=0)
| returns reference to the specified element (nD case)
template<typename _Tp >
_Tp | value (int i0, size_t *hashval=0) const
| returns value of the specified element (1D case)
template<typename _Tp >
_Tp | value (int i0, int i1, size_t *hashval=0) const
| returns value of the specified element (2D case)
template<typename _Tp >
_Tp | value (int i0, int i1, int i2, size_t *hashval=0) const
| returns value of the specified element (3D case)
template<typename _Tp >
_Tp | value (const int *idx, size_t *hashval=0) const
| returns value of the specified element (nD case)
template<typename _Tp >
const _Tp * | find (int i0, size_t *hashval=0) const
| returns pointer to the specified element (1D case)
template<typename _Tp >
const _Tp * | find (int i0, int i1, size_t *hashval=0) const
| returns pointer to the specified element (2D case)
template<typename _Tp >
const _Tp * | find (int i0, int i1, int i2, size_t *hashval=0) const
| returns pointer to the specified element (3D case)
template<typename _Tp >
const _Tp * | find (const int *idx, size_t *hashval=0) const
| returns pointer to the specified element (nD case)
void | erase (int i0, int i1, size_t *hashval=0)
| erases the specified element (2D case)
void | erase (int i0, int i1, int i2, size_t *hashval=0)
| erases the specified element (3D case)
void | erase (const int *idx, size_t *hashval=0)
| erases the specified element (nD case)
SparseMatIterator | begin ()
| returns the sparse matrix iterator at the matrix beginning
template<typename _Tp >
SparseMatIterator_< _Tp > | begin ()
| returns the sparse matrix iterator at the matrix beginning
SparseMatConstIterator | begin () const
| returns the read-only sparse matrix iterator at the matrix beginning
template<typename _Tp >
SparseMatConstIterator_< _Tp > | begin () const
| returns the read-only sparse matrix iterator at the matrix beginning

## Public Attributes

int | flags
Hdr * | hdr

## Detailed Description

Sparse matrix class.

The class represents multi-dimensional sparse numerical arrays. Such a sparse array can store elements of any type that cv::Mat is able to store. "Sparse" means that only non-zero elements are stored (though, as a result of some operations on a sparse matrix, some of its stored elements can actually become 0. It's user responsibility to detect such elements and delete them using cv::SparseMat::erase(). The non-zero elements are stored in a hash table that grows when it's filled enough, so that the search time remains O(1) in average. Elements can be accessed using the following methods:

1. Query operations: cv::SparseMat::ptr() and the higher-level cv::SparseMat::ref(), cv::SparseMat::value() and cv::SparseMat::find, for example:

        const int dims = 5;
        int size[] = {10, 10, 10, 10, 10};
        SparseMat sparse_mat(dims, size, CV_32F);
        for(int i = 0; i < 1000; i++)
        {
            int idx[dims];
            for(int k = 0; k < dims; k++)
               idx[k] = rand()%sparse_mat.size(k);
            sparse_mat.ref<float>(idx) += 1.f;
        }

2. Sparse matrix iterators. Like cv::Mat iterators and unlike cv::Mat iterators, the sparse matrix iterators are STL-style, that is, the iteration is done as following:

        // prints elements of a sparse floating-point matrix and the sum of elements.
        SparseMatConstIterator_<float>
               it = sparse_mat.begin<float>(),
               it_end = sparse_mat.end<float>();
        double s = 0;
        int dims = sparse_mat.dims();
        for(; it != it_end; ++it)
        {
            // print element indices and the element value
            const Node* n = it.node();
            printf("(")
            for(int i = 0; i < dims; i++)
               printf("%3d%c", n->idx[i], i < dims-1 ? ',' : ')');
            printf(": %f\n", *it);
            s += *it;
        }
        printf("Element sum is %g\n", s);

   If you run this loop, you will notice that elements are enumerated in no any logical order (lexicographical etc.), they come in the same order as they stored in the hash table, i.e. semi-randomly.

   You may collect pointers to the nodes and sort them to get the proper ordering. Note, however, that pointers to the nodes may become invalid when you add more elements to the matrix; this is because of possible buffer reallocation.

3. A combination of the above 2 methods when you need to process 2 or more sparse matrices simultaneously, e.g. this is how you can compute unnormalized cross-correlation of the 2 floating-point sparse matrices:

        double crossCorr(const SparseMat& a, const SparseMat& b)
        {
            const SparseMat *_a = &a, *_b = &b;
            // if b contains less elements than a,
            // it's faster to iterate through b
            if(_a->nzcount() > _b->nzcount())
               std::swap(_a, _b);
            SparseMatConstIterator_<float> it = _a->begin<float>(),
                                           it_end = _a->end<float>();
            double ccorr = 0;
            for(; it != it_end; ++it)
            {
                // take the next element from the first matrix
                float avalue = *it;
                const Node* anode = it.node();
                // and try to find element with the same index in the second matrix.
                // since the hash value depends only on the element index,
                // we reuse hashvalue stored in the node
                float bvalue = _b->value<float>(anode->idx,&anode->hashval);
                ccorr += avalue*bvalue;
            }
            return ccorr;
        }

## Member Typedef Documentation

typedef SparseMatConstIterator cv::SparseMat::const_iterator

Reimplemented in cv::SparseMat_< _Tp >.

typedef SparseMatIterator cv::SparseMat::iterator

Reimplemented in cv::SparseMat_< _Tp >.

## Member Enumeration Documentation

anonymous enum

Enumerator:

  MAGIC_VAL |
  MAX_DIM |
  HASH_SCALE |
  HASH_BIT |

## Constructor & Destructor Documentation

cv::SparseMat::SparseMat | ( | ) | `[inline]`

default constructor

cv::SparseMat::SparseMat | ( | int | dims,
|  | const int * | _sizes,
|  | int | _type
| ) |  | `[inline]`

creates matrix of the specified size and type

cv::SparseMat::SparseMat | ( | const SparseMat & | m ) | `[inline]`

copy constructor

cv::SparseMat::SparseMat | ( | const Mat & | m ) |

converts dense 2d matrix to the sparse form

Parameters:

  m | the input matrix
  try1d | if true and m is a single-column matrix (Nx1), then the sparse matrix will be 1-dimensional.

cv::SparseMat::SparseMat | ( | const CvSparseMat * | m ) |

converts old-style sparse matrix to the new-style. All the data is copied

cv::SparseMat::~SparseMat | ( | ) | `[inline]`

the destructor

## Member Function Documentation

void cv::SparseMat::addref | ( | ) | `[inline]`

manually increments the reference counter to the header.

void cv::SparseMat::assignTo | ( | SparseMat & | m,
|  | int | type = `-1`
| ) |  | const`[inline]`

SparseMatIterator_< _Tp > cv::SparseMat::begin | ( | ) | `[inline]`

returns the sparse matrix iterator at the matrix beginning

return the sparse matrix iterator pointing to the first sparse matrix element

Reimplemented in cv::SparseMat_< _Tp >.

template<typename _Tp >

SparseMatIterator_<_Tp> cv::SparseMat::begin | ( | ) |

returns the sparse matrix iterator at the matrix beginning

Reimplemented in cv::SparseMat_< _Tp >.

SparseMatConstIterator_< _Tp > cv::SparseMat::begin | ( | ) | const`[inline]`

returns the read-only sparse matrix iterator at the matrix beginning

Reimplemented in cv::SparseMat_< _Tp >.

template<typename _Tp >

SparseMatConstIterator_<_Tp> cv::SparseMat::begin | ( | ) | const

returns the read-only sparse matrix iterator at the matrix beginning

Reimplemented in cv::SparseMat_< _Tp >.

int cv::SparseMat::channels | ( | ) | const`[inline]`

returns the number of channels

Reimplemented in cv::SparseMat_< _Tp >.

void cv::SparseMat::clear | ( | ) |

sets all the sparse matrix elements to 0, which means clearing the hash table.

SparseMat cv::SparseMat::clone | ( | ) | const`[inline]`

creates full copy of the matrix

Reimplemented in cv::SparseMat_< _Tp >.

void cv::SparseMat::convertTo | ( | SparseMat & | m,
|  | int | rtype,
|  | double | alpha = `1`
| ) |  | const

multiplies all the matrix elements by the specified scale factor alpha and converts the results to the specified data type

void cv::SparseMat::convertTo | ( | Mat & | m,
|  | int | rtype,
|  | double | alpha = `1`,
|  | double | beta = `0`
| ) |  | const

converts sparse matrix to dense n-dim matrix with optional type conversion and scaling.

Parameters:

  rtype | The output matrix data type. When it is =-1, the output array will have the same data type as (*this)
  alpha | The scale factor
  beta | The optional delta added to the scaled values before the conversion

void cv::SparseMat::copyTo | ( | SparseMat & | m ) | const

copies all the data to the destination matrix. All the previous content of m is erased

void cv::SparseMat::copyTo | ( | Mat & | m ) | const

converts sparse matrix to dense matrix.

void cv::SparseMat::create | ( | int | dims,
|  | const int * | _sizes,
|  | int | _type
| ) |  |

reallocates sparse matrix.

If the matrix already had the proper size and type, it is simply cleared with clear(), otherwise, the old matrix is released (using release()) and the new one is allocated.

int cv::SparseMat::depth | ( | ) | const`[inline]`

returns the depth of sparse matrix elements

Reimplemented in cv::SparseMat_< _Tp >.

int cv::SparseMat::dims | ( | ) | const`[inline]`

returns the matrix dimensionality

size_t cv::SparseMat::elemSize | ( | ) | const`[inline]`

returns the size of each element in bytes (not including the overhead - the space occupied by SparseMat::Node elements)

size_t cv::SparseMat::elemSize1 | ( | ) | const`[inline]`

returns elemSize()/channels()

SparseMatIterator_< _Tp > cv::SparseMat::end | ( | ) | `[inline]`

returns the sparse matrix iterator at the matrix end

return the sparse matrix iterator pointing to the element following the last sparse matrix element

Reimplemented in cv::SparseMat_< _Tp >.

SparseMatConstIterator_< _Tp > cv::SparseMat::end | ( | ) | const`[inline]`

returns the read-only sparse matrix iterator at the matrix end

Reimplemented in cv::SparseMat_< _Tp >.

template<typename _Tp >

SparseMatIterator_<_Tp> cv::SparseMat::end | ( | ) |

returns the typed sparse matrix iterator at the matrix end

Reimplemented in cv::SparseMat_< _Tp >.

template<typename _Tp >

SparseMatConstIterator_<_Tp> cv::SparseMat::end | ( | ) | const

returns the typed read-only sparse matrix iterator at the matrix end

Reimplemented in cv::SparseMat_< _Tp >.

void cv::SparseMat::erase | ( | int | i0,
|  | int | i1,
|  | size_t * | hashval = `0`
| ) |  |

erases the specified element (2D case)

void cv::SparseMat::erase | ( | int | i0,
|  | int | i1,
|  | int | i2,
|  | size_t * | hashval = `0`
| ) |  |

erases the specified element (3D case)

void cv::SparseMat::erase | ( | const int * | idx,
|  | size_t * | hashval = `0`
| ) |  |

erases the specified element (nD case)

template<typename _Tp >

const _Tp * cv::SparseMat::find | ( | int | i0,
|  | size_t * | hashval = `0`
| ) |  | const`[inline]`

returns pointer to the specified element (1D case)

Return pointer to the specified sparse matrix element if it exists

find<_Tp>(i0,...[,hashval]) is equivalent to (_const Tp*)ptr(i0,...false[,hashval]).

If the specified element does not exist, the methods return NULL.

template<typename _Tp >

const _Tp * cv::SparseMat::find | ( | int | i0,
|  | int | i1,
|  | size_t * | hashval = `0`
| ) |  | const`[inline]`

returns pointer to the specified element (2D case)

template<typename _Tp >

const _Tp * cv::SparseMat::find | ( | int | i0,
|  | int | i1,
|  | int | i2,
|  | size_t * | hashval = `0`
| ) |  | const`[inline]`

returns pointer to the specified element (3D case)

template<typename _Tp >

const _Tp * cv::SparseMat::find | ( | const int * | idx,
|  | size_t * | hashval = `0`
| ) |  | const`[inline]`

returns pointer to the specified element (nD case)

size_t cv::SparseMat::hash | ( | int | i0,
|  | int | i1,
|  | int | i2
| ) |  | const`[inline]`

computes the element hash value (3D case)

size_t cv::SparseMat::hash | ( | const int * | idx ) | const`[inline]`

computes the element hash value (nD case)

size_t cv::SparseMat::hash | ( | int | i0 ) | const`[inline]`

computes the element hash value (1D case)

size_t cv::SparseMat::hash | ( | int | i0,
|  | int | i1
| ) |  | const`[inline]`

computes the element hash value (2D case)

uchar* cv::SparseMat::newNode | ( | const int * | idx,
|  | size_t | hashval
| ) |  |

const SparseMat::Node * cv::SparseMat::node | ( | size_t | nidx ) | const`[inline]`

SparseMat::Node * cv::SparseMat::node | ( | size_t | nidx ) | `[inline]`

size_t cv::SparseMat::nzcount | ( | ) | const`[inline]`

returns the number of non-zero elements (=the number of hash table nodes)

cv::SparseMat::operator CvSparseMat * | ( | ) | const

converts sparse matrix to the old-style representation; all the elements are copied.

Reimplemented in cv::SparseMat_< _Tp >.

SparseMat & cv::SparseMat::operator= | ( | const Mat & | m ) | `[inline]`

equivalent to the corresponding constructor

Reimplemented in cv::SparseMat_< _Tp >.

SparseMat & cv::SparseMat::operator= | ( | const SparseMat & | m ) | `[inline]`

assignment operator. This is O(1) operation, i.e. no data is copied

Reimplemented in cv::SparseMat_< _Tp >.

uchar* cv::SparseMat::ptr | ( | int | i0,
|  | int | i1,
|  | int | i2,
|  | bool | createMissing,
|  | size_t * | hashval = `0`
| ) |  |

returns pointer to the specified element (3D case)

uchar* cv::SparseMat::ptr | ( | const int * | idx,
|  | bool | createMissing,
|  | size_t * | hashval = `0`
| ) |  |

returns pointer to the specified element (nD case)

uchar* cv::SparseMat::ptr | ( | int | i0,
|  | bool | createMissing,
|  | size_t * | hashval = `0`
| ) |  |

returns pointer to the specified element (1D case)

specialized variants for 1D, 2D, 3D cases and the generic_type one for n-D case.

return pointer to the matrix element.

- if the element is there (it's non-zero), the pointer to it is returned
- if it's not there and createMissing=false, NULL pointer is returned
- if it's not there and createMissing=true, then the new element is created and initialized with 0. Pointer to it is returned
- if the optional hashval pointer is not NULL, the element hash value is not computed, but *hashval is taken instead.

uchar* cv::SparseMat::ptr | ( | int | i0,
|  | int | i1,
|  | bool | createMissing,
|  | size_t * | hashval = `0`
| ) |  |

returns pointer to the specified element (2D case)

template<typename _Tp >

_Tp & cv::SparseMat::ref | ( | int | i0,
|  | int | i1,
|  | size_t * | hashval = `0`
| ) |  | `[inline]`

returns reference to the specified element (2D case)

Reimplemented in cv::SparseMat_< _Tp >.

template<typename _Tp >

_Tp & cv::SparseMat::ref | ( | const int * | idx,
|  | size_t * | hashval = `0`
| ) |  | `[inline]`

returns reference to the specified element (nD case)

Reimplemented in cv::SparseMat_< _Tp >.

template<typename _Tp >

_Tp & cv::SparseMat::ref | ( | int | i0,
|  | int | i1,
|  | int | i2,
|  | size_t * | hashval = `0`
| ) |  | `[inline]`

returns reference to the specified element (3D case)

Reimplemented in cv::SparseMat_< _Tp >.

template<typename _Tp >

_Tp & cv::SparseMat::ref | ( | int | i0,
|  | size_t * | hashval = `0`
| ) |  | `[inline]`

returns reference to the specified element (1D case)

return read-write reference to the specified sparse matrix element.

ref<_Tp>(i0,...[,hashval]) is equivalent to *(_Tp*)ptr(i0,...,true[,hashval]). The methods always return a valid reference. If the element did not exist, it is created and initialiazed with 0.

Reimplemented in cv::SparseMat_< _Tp >.

void cv::SparseMat::release | ( | ) | `[inline]`

void cv::SparseMat::removeNode | ( | size_t | hidx,
|  | size_t | nidx,
|  | size_t | previdx
| ) |  |

void cv::SparseMat::resizeHashTab | ( | size_t | newsize ) |

const int * cv::SparseMat::size | ( | ) | const`[inline]`

returns the array of sizes, or NULL if the matrix is not allocated

int cv::SparseMat::size | ( | int | i ) | const`[inline]`

returns the size of i-th matrix dimension (or 0)

int cv::SparseMat::type | ( | ) | const`[inline]`

returns type of sparse matrix elements

Reimplemented in cv::SparseMat_< _Tp >.

template<typename _Tp >

_Tp cv::SparseMat::value | ( | int | i0,
|  | int | i1,
|  | int | i2,
|  | size_t * | hashval = `0`
| ) |  | const`[inline]`

returns value of the specified element (3D case)

template<typename _Tp >

_Tp & cv::SparseMat::value | ( | Node * | n ) | `[inline]`

returns the value stored in the sparse martix node

template<typename _Tp >

_Tp cv::SparseMat::value | ( | int | i0,
|  | size_t * | hashval = `0`
| ) |  | const`[inline]`

returns value of the specified element (1D case)

return value of the specified sparse matrix element.

value<_Tp>(i0,...[,hashval]) is equivalent

         { const _Tp* p = find<_Tp>(i0,...[,hashval]); return p ? *p : _Tp(); }

That is, if the element did not exist, the methods return 0.

template<typename _Tp >

_Tp cv::SparseMat::value | ( | const int * | idx,
|  | size_t * | hashval = `0`
| ) |  | const`[inline]`

returns value of the specified element (nD case)

template<typename _Tp >

_Tp cv::SparseMat::value | ( | int | i0,
|  | int | i1,
|  | size_t * | hashval = `0`
| ) |  | const`[inline]`

returns value of the specified element (2D case)

template<typename _Tp >

const _Tp & cv::SparseMat::value | ( | const Node * | n ) | const`[inline]`

returns the value stored in the sparse martix node

## Member Data Documentation

int cv::SparseMat::flags

Hdr* cv::SparseMat::hdr

The documentation for this class was generated from the following files:

- /usr/ports/pobj/OpenCV-2.2.0/OpenCV-2.2.0/modules/core/include/opencv2/core/core.hpp
- /usr/ports/pobj/OpenCV-2.2.0/OpenCV-2.2.0/modules/core/include/opencv2/core/mat.hpp

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