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Public Member Functions | Public Attributes | Protected Attributes | List of all members
cv::NAryMatIterator Class Reference

n-ary multi-dimensional array iterator. More...

#include <mat.hpp>

Public Member Functions

 NAryMatIterator ()
 the default constructor
 
 NAryMatIterator (const Mat **arrays, uchar **ptrs, int narrays=-1)
 the full constructor taking arbitrary number of n-dim matrices
 
 NAryMatIterator (const Mat **arrays, Mat *planes, int narrays=-1)
 the full constructor taking arbitrary number of n-dim matrices
 
void init (const Mat **arrays, Mat *planes, uchar **ptrs, int narrays=-1)
 the separate iterator initialization method
 
NAryMatIteratoroperator++ ()
 proceeds to the next plane of every iterated matrix
 
NAryMatIterator operator++ (int)
 proceeds to the next plane of every iterated matrix (postfix increment operator)
 

Public Attributes

const Mat ** arrays
 the iterated arrays
 
Matplanes
 the current planes
 
uchar ** ptrs
 data pointers
 
int narrays
 the number of arrays
 
size_t nplanes
 the number of hyper-planes that the iterator steps through
 
size_t size
 the size of each segment (in elements)
 

Protected Attributes

int iterdepth
 
size_t idx
 

Detailed Description

n-ary multi-dimensional array iterator.

Use the class to implement unary, binary, and, generally, n-ary element-wise operations on multi-dimensional arrays. Some of the arguments of an n-ary function may be continuous arrays, some may be not. It is possible to use conventional MatIterator 's for each array but incrementing all of the iterators after each small operations may be a big overhead. In this case consider using NAryMatIterator to iterate through several matrices simultaneously as long as they have the same geometry (dimensionality and all the dimension sizes are the same). On each iteration it.planes[0], it.planes[1],... will be the slices of the corresponding matrices.

The example below illustrates how you can compute a normalized and threshold 3D color histogram:

void computeNormalizedColorHist(const Mat& image, Mat& hist, int N, double minProb)
{
const int histSize[] = {N, N, N};
// make sure that the histogram has a proper size and type
hist.create(3, histSize, CV_32F);
// and clear it
hist = Scalar(0);
// the loop below assumes that the image
// is a 8-bit 3-channel. check it.
CV_Assert(image.type() == CV_8UC3);
it_end = image.end<Vec3b>();
for( ; it != it_end; ++it )
{
const Vec3b& pix = *it;
hist.at<float>(pix[0]*N/256, pix[1]*N/256, pix[2]*N/256) += 1.f;
}
minProb *= image.rows*image.cols;
// initialize iterator (the style is different from STL).
// after initialization the iterator will contain
// the number of slices or planes the iterator will go through.
// it simultaneously increments iterators for several matrices
// supplied as a null terminated list of pointers
const Mat* arrays[] = {&hist, 0};
Mat planes[1];
double s = 0;
// iterate through the matrix. on each iteration
// itNAry.planes[i] (of type Mat) will be set to the current plane
// of the i-th n-dim matrix passed to the iterator constructor.
for(int p = 0; p < itNAry.nplanes; p++, ++itNAry)
{
threshold(itNAry.planes[0], itNAry.planes[0], minProb, 0, THRESH_TOZERO);
s += sum(itNAry.planes[0])[0];
}
s = 1./s;
itNAry = NAryMatIterator(arrays, planes, 1);
for(int p = 0; p < itNAry.nplanes; p++, ++itNAry)
itNAry.planes[0] *= s;
}
Matrix read-only iterator.
Definition mat.hpp:3149
n-dimensional dense array class
Definition mat.hpp:812
const Mat ** arrays
the iterated arrays
Definition mat.hpp:3478
Mat * planes
the current planes
Definition mat.hpp:3480
NAryMatIterator()
the default constructor
Template class for short numerical vectors, a partial case of Matx.
Definition matx.hpp:369
Scalar_< double > Scalar
Definition types.hpp:702
#define CV_32F
Definition interface.h:78
#define CV_8UC3
Definition interface.h:90
#define CV_Assert(expr)
Checks a condition at runtime and throws exception if it fails.
Definition base.hpp:342
double threshold
Definition imgproc_c.h:712
int CvHistogram * hist
Definition imgproc_c.h:653
OutputArray sum
Definition imgproc.hpp:2882
@ THRESH_TOZERO
Definition imgproc.hpp:328
const IplImage * image
Definition videoio_c.h:131

Constructor & Destructor Documentation

◆ NAryMatIterator() [1/3]

cv::NAryMatIterator::NAryMatIterator ( )

the default constructor

◆ NAryMatIterator() [2/3]

cv::NAryMatIterator::NAryMatIterator ( const Mat **  arrays,
uchar **  ptrs,
int  narrays = -1 
)

the full constructor taking arbitrary number of n-dim matrices

◆ NAryMatIterator() [3/3]

cv::NAryMatIterator::NAryMatIterator ( const Mat **  arrays,
Mat planes,
int  narrays = -1 
)

the full constructor taking arbitrary number of n-dim matrices

Member Function Documentation

◆ init()

void cv::NAryMatIterator::init ( const Mat **  arrays,
Mat planes,
uchar **  ptrs,
int  narrays = -1 
)

the separate iterator initialization method

◆ operator++() [1/2]

NAryMatIterator & cv::NAryMatIterator::operator++ ( )

proceeds to the next plane of every iterated matrix

◆ operator++() [2/2]

NAryMatIterator cv::NAryMatIterator::operator++ ( int  )

proceeds to the next plane of every iterated matrix (postfix increment operator)

Member Data Documentation

◆ arrays

const Mat** cv::NAryMatIterator::arrays

the iterated arrays

◆ idx

size_t cv::NAryMatIterator::idx
protected

◆ iterdepth

int cv::NAryMatIterator::iterdepth
protected

◆ narrays

int cv::NAryMatIterator::narrays

the number of arrays

◆ nplanes

size_t cv::NAryMatIterator::nplanes

the number of hyper-planes that the iterator steps through

◆ planes

Mat* cv::NAryMatIterator::planes

the current planes

◆ ptrs

uchar** cv::NAryMatIterator::ptrs

data pointers

◆ size

size_t cv::NAryMatIterator::size

the size of each segment (in elements)


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