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java.lang.Object org.opencv.core.Mat
public class Mat
OpenCV C++ ndimensional dense array class
class CV_EXPORTS Mat
// C++ code:
public:
//... a lot of methods......
/ *! includes several bitfields:
 the magic signature
 continuity flag
 depth
 number of channels
 /
int flags;
//! the array dimensionality, >= 2
int dims;
//! the number of rows and columns or (1, 1) when the array has more than 2
dimensions
int rows, cols;
//! pointer to the data
uchar* data;
//! pointer to the reference counter;
// when array points to userallocated data, the pointer is NULL
int* refcount;
// other members...
};
The class
Mat
represents an ndimensional dense numerical
singlechannel or multichannel array. It can be used to store real or
complexvalued vectors and matrices, grayscale or color images, voxel
volumes, vector fields, point clouds, tensors, histograms (though, very
highdimensional histograms may be better stored in a SparseMat
).
The data layout of the array
M is defined by the array M.step[]
, so that the address
of element (i_0,...,i_(M.dims1)), where 0 <= i_k<M.size[k],
is computed as:
addr(M_(i_0,...,i_(M.dims1))) = M.data + M.step[0]*i_0 + M.step[1]*i_1 +... + M.step[M.dims1]*i_(M.dims1)
In case of a 2dimensional array, the above formula is reduced to:
addr(M_(i,j)) = M.data + M.step[0]*i + M.step[1]*j
Note that M.step[i] >= M.step[i+1]
(in fact, M.step[i] >=
M.step[i+1]*M.size[i+1]
). This means that 2dimensional matrices are
stored rowbyrow, 3dimensional matrices are stored planebyplane, and so
on. M.step[M.dims1]
is minimal and always equal to the element
size M.elemSize()
.
So, the data layout in Mat
is fully compatible with
CvMat
, IplImage
, and CvMatND
types
from OpenCV 1.x. It is also compatible with the majority of dense array types
from the standard toolkits and SDKs, such as Numpy (ndarray), Win32
(independent device bitmaps), and others, that is, with any array that uses
*steps* (or *strides*) to compute the position of a pixel. Due to this
compatibility, it is possible to make a Mat
header for
userallocated data and process it inplace using OpenCV functions.
There are many different ways to create a Mat
object. The most
popular options are listed below:
create(nrows, ncols, type)
method or the similar
Mat(nrows, ncols, type[, fillValue])
constructor. A new array of
the specified size and type is allocated. type
has the same
meaning as in the cvCreateMat
method.
For example, CV_8UC1
means a 8bit singlechannel array,
CV_32FC2
means a 2channel (complex) floatingpoint array, and
so on.
// C++ code:
// make a 7x7 complex matrix filled with 1+3j.
Mat M(7,7,CV_32FC2,Scalar(1,3));
// and now turn M to a 100x60 15channel 8bit matrix.
// The old content will be deallocated
M.create(100,60,CV_8UC(15));
As noted in the introduction to this chapter, create()
allocates
only a new array when the shape or type of the current array are different
from the specified ones.
// C++ code:
// create a 100x100x100 8bit array
int sz[] = {100, 100, 100};
Mat bigCube(3, sz, CV_8U, Scalar.all(0));
It passes the number of dimensions =1 to the Mat
constructor but
the created array will be 2dimensional with the number of columns set to 1.
So, Mat.dims
is always >= 2 (can also be 0 when the array is
empty).
Mat.clone()
method can be used to get a full (deep) copy of the array when you need it.
// C++ code:
// add the 5th row, multiplied by 3 to the 3rd row
M.row(3) = M.row(3) + M.row(5)*3;
// now copy the 7th column to the 1st column
// M.col(1) = M.col(7); // this will not work
Mat M1 = M.col(1);
M.col(7).copyTo(M1);
// create a new 320x240 image
Mat img(Size(320,240),CV_8UC3);
// select a ROI
Mat roi(img, Rect(10,10,100,100));
// fill the ROI with (0,255,0) (which is green in RGB space);
// the original 320x240 image will be modified
roi = Scalar(0,255,0);
Due to the additional datastart
and dataend
members, it is possible to compute a relative subarray position in the main
*container* array using locateROI()
:
// C++ code:
Mat A = Mat.eye(10, 10, CV_32S);
// extracts A columns, 1 (inclusive) to 3 (exclusive).
Mat B = A(Range.all(), Range(1, 3));
// extracts B rows, 5 (inclusive) to 9 (exclusive).
// that is, C ~ A(Range(5, 9), Range(1, 3))
Mat C = B(Range(5, 9), Range.all());
Size size; Point ofs;
C.locateROI(size, ofs);
// size will be (width=10,height=10) and the ofs will be (x=1, y=5)
As in case of whole matrices, if you need a deep copy, use the
clone()
method of the extracted submatrices.
gstreamer
, and so
on). For example:
// C++ code:
void process_video_frame(const unsigned char* pixels,
int width, int height, int step)
Mat img(height, width, CV_8UC3, pixels, step);
GaussianBlur(img, img, Size(7,7), 1.5, 1.5);
// C++ code:
double m[3][3] = {{a, b, c}, {d, e, f}, {g, h, i}};
Mat M = Mat(3, 3, CV_64F, m).inv();
Partial yet very common cases of this *userallocated data* case are
conversions from CvMat
and IplImage
to
Mat
. For this purpose, there are special constructors taking
pointers to CvMat
or IplImage
and the optional flag
indicating whether to copy the data or not.
Backward conversion from Mat
to CvMat
or
IplImage
is provided via cast operators Mat.operator
CvMat() const
and Mat.operator IplImage()
. The operators
do NOT copy the data.
// C++ code:
IplImage* img = cvLoadImage("greatwave.jpg", 1);
Mat mtx(img); // convert IplImage* > Mat
CvMat oldmat = mtx; // convert Mat > CvMat
CV_Assert(oldmat.cols == img>width && oldmat.rows == img>height &&
oldmat.data.ptr == (uchar*)img>imageData && oldmat.step == img>widthStep);
zeros(), ones(),
eye()
, for example:
// C++ code:
// create a doubleprecision identity martix and add it to M.
M += Mat.eye(M.rows, M.cols, CV_64F);
// C++ code:
// create a 3x3 doubleprecision identity matrix
Mat M = (Mat_(3,3) << 1, 0, 0, 0, 1, 0, 0, 0, 1);
With this approach, you first call a constructor of the "Mat_" class with the
proper parameters, and then you just put <<
operator followed by
commaseparated values that can be constants, variables, expressions, and so
on. Also, note the extra parentheses required to avoid compilation errors.
Once the array is created, it is automatically managed via a
referencecounting mechanism. If the array header is built on top of
userallocated data, you should handle the data by yourself.
The array data is deallocated when no one points to it. If you want to
release the data pointed by a array header before the array destructor is
called, use Mat.release()
.
The next important thing to learn about the array class is element access.
This manual already described how to compute an address of each array
element. Normally, you are not required to use the formula directly in the
code. If you know the array element type (which can be retrieved using the
method Mat.type()
), you can access the elementM_(ij)
of a 2dimensional array as:
// C++ code:
M.at(i,j) += 1.f;
assuming that M is a doubleprecision floatingpoint array. There are several
variants of the method
at
for a different number of dimensions.
If you need to process a whole row of a 2D array, the most efficient way is
to get the pointer to the row first, and then just use the plain C operator
[]
:
// C++ code:
// compute sum of positive matrix elements
// (assuming that M isa doubleprecision matrix)
double sum=0;
for(int i = 0; i < M.rows; i++)
const double* Mi = M.ptr(i);
for(int j = 0; j < M.cols; j++)
sum += std.max(Mi[j], 0.);
Some operations, like the one above, do not actually depend on the array
shape. They just process elements of an array one by one (or elements from
multiple arrays that have the same coordinates, for example, array addition).
Such operations are called *elementwise*. It makes sense to check whether
all the input/output arrays are continuous, namely, have no gaps at the end
of each row. If yes, process them as a long single row:
// compute the sum of positive matrix elements, optimized variant
double sum=0;
int cols = M.cols, rows = M.rows;
if(M.isContinuous())
cols *= rows;
rows = 1;
for(int i = 0; i < rows; i++)
const double* Mi = M.ptr(i);
for(int j = 0; j < cols; j++)
sum += std.max(Mi[j], 0.);
In case of the continuous matrix, the outer loop body is executed just once.
So, the overhead is smaller, which is especially noticeable in case of small
matrices.
Finally, there are STLstyle iterators that are smart enough to skip gaps
between successive rows:
// C++ code:
// compute sum of positive matrix elements, iteratorbased variant
double sum=0;
MatConstIterator_ it = M.begin(), it_end = M.end();
for(; it != it_end; ++it)
sum += std.max(*it, 0.);
The matrix iterators are randomaccess iterators, so they can be passed to
any STL algorithm, including
std.sort()
.
Field Summary  

long 
nativeObj

Constructor Summary  

Mat()
Various Mat constructors These are various constructors that form a matrix. 

Mat(int rows,
int cols,
int type)
Various Mat constructors These are various constructors that form a matrix. 

Mat(int rows,
int cols,
int type,
Scalar s)
Various Mat constructors These are various constructors that form a matrix. 

Mat(long addr)


Mat(Mat m,
Range rowRange)
Various Mat constructors These are various constructors that form a matrix. 

Mat(Mat m,
Range rowRange,
Range colRange)
Various Mat constructors These are various constructors that form a matrix. 

Mat(Mat m,
Rect roi)
Various Mat constructors These are various constructors that form a matrix. 

Mat(Size size,
int type)
Various Mat constructors These are various constructors that form a matrix. 

Mat(Size size,
int type,
Scalar s)
Various Mat constructors These are various constructors that form a matrix. 
Method Summary  

Mat 
adjustROI(int dtop,
int dbottom,
int dleft,
int dright)
Adjusts a submatrix size and position within the parent matrix. 
void 
assignTo(Mat m)
Provides a functional form of convertTo . 
void 
assignTo(Mat m,
int type)
Provides a functional form of convertTo . 
int 
channels()
Returns the number of matrix channels. 
int 
checkVector(int elemChannels)

int 
checkVector(int elemChannels,
int depth)

int 
checkVector(int elemChannels,
int depth,
boolean requireContinuous)

Mat 
clone()
Creates a full copy of the array and the underlying data. 
Mat 
col(int x)
Creates a matrix header for the specified matrix column. 
Mat 
colRange(int startcol,
int endcol)
Creates a matrix header for the specified row span. 
Mat 
colRange(Range r)
Creates a matrix header for the specified row span. 
int 
cols()

void 
convertTo(Mat m,
int rtype)
Converts an array to another data type with optional scaling. 
void 
convertTo(Mat m,
int rtype,
double alpha)
Converts an array to another data type with optional scaling. 
void 
convertTo(Mat m,
int rtype,
double alpha,
double beta)
Converts an array to another data type with optional scaling. 
void 
copyTo(Mat m)
Copies the matrix to another one. 
void 
copyTo(Mat m,
Mat mask)
Copies the matrix to another one. 
void 
create(int rows,
int cols,
int type)
Allocates new array data if needed. 
void 
create(Size size,
int type)
Allocates new array data if needed. 
Mat 
cross(Mat m)
Computes a crossproduct of two 3element vectors. 
long 
dataAddr()

int 
depth()
Returns the depth of a matrix element. 
Mat 
diag()
Extracts a diagonal from a matrix, or creates a diagonal matrix. 
Mat 
diag(int d)
Extracts a diagonal from a matrix, or creates a diagonal matrix. 
static Mat 
diag(Mat d)
Extracts a diagonal from a matrix, or creates a diagonal matrix. 
double 
dot(Mat m)
Computes a dotproduct of two vectors. 
java.lang.String 
dump()

long 
elemSize()
Returns the matrix element size in bytes. 
long 
elemSize1()
Returns the size of each matrix element channel in bytes. 
boolean 
empty()
Returns true if the array has no elements. 
static Mat 
eye(int rows,
int cols,
int type)
Returns an identity matrix of the specified size and type. 
static Mat 
eye(Size size,
int type)
Returns an identity matrix of the specified size and type. 
protected void 
finalize()

double[] 
get(int row,
int col)

int 
get(int row,
int col,
byte[] data)

int 
get(int row,
int col,
double[] data)

int 
get(int row,
int col,
float[] data)

int 
get(int row,
int col,
int[] data)

int 
get(int row,
int col,
short[] data)

long 
getNativeObjAddr()

int 
height()

Mat 
inv()
Inverses a matrix. 
Mat 
inv(int method)
Inverses a matrix. 
boolean 
isContinuous()
Reports whether the matrix is continuous or not. 
boolean 
isSubmatrix()

void 
locateROI(Size wholeSize,
Point ofs)
Locates the matrix header within a parent matrix. 
Mat 
mul(Mat m)
Performs an elementwise multiplication or division of the two matrices. 
Mat 
mul(Mat m,
double scale)
Performs an elementwise multiplication or division of the two matrices. 
static Mat 
ones(int rows,
int cols,
int type)
Returns an array of all 1's of the specified size and type. 
static Mat 
ones(Size size,
int type)
Returns an array of all 1's of the specified size and type. 
void 
push_back(Mat m)
Adds elements to the bottom of the matrix. 
int 
put(int row,
int col,
byte[] data)

int 
put(int row,
int col,
double... data)

int 
put(int row,
int col,
float[] data)

int 
put(int row,
int col,
int[] data)

int 
put(int row,
int col,
short[] data)

void 
release()
Decrements the reference counter and deallocates the matrix if needed. 
Mat 
reshape(int cn)
Changes the shape and/or the number of channels of a 2D matrix without copying the data. 
Mat 
reshape(int cn,
int rows)
Changes the shape and/or the number of channels of a 2D matrix without copying the data. 
Mat 
row(int y)
Creates a matrix header for the specified matrix row. 
Mat 
rowRange(int startrow,
int endrow)
Creates a matrix header for the specified row span. 
Mat 
rowRange(Range r)
Creates a matrix header for the specified row span. 
int 
rows()

Mat 
setTo(Mat value)
Sets all or some of the array elements to the specified value. 
Mat 
setTo(Mat value,
Mat mask)
Sets all or some of the array elements to the specified value. 
Mat 
setTo(Scalar s)

Mat 
setTo(Scalar value,
Mat mask)
Sets all or some of the array elements to the specified value. 
Size 
size()
Returns a matrix size. 
long 
step1()
Returns a normalized step. 
long 
step1(int i)
Returns a normalized step. 
Mat 
submat(int rowStart,
int rowEnd,
int colStart,
int colEnd)
Extracts a rectangular submatrix. 
Mat 
submat(Range rowRange,
Range colRange)
Extracts a rectangular submatrix. 
Mat 
submat(Rect roi)
Extracts a rectangular submatrix. 
Mat 
t()
Transposes a matrix. 
java.lang.String 
toString()

long 
total()
Returns the total number of array elements. 
int 
type()
Returns the type of a matrix element. 
int 
width()

static Mat 
zeros(int rows,
int cols,
int type)
Returns a zero array of the specified size and type. 
static Mat 
zeros(Size size,
int type)
Returns a zero array of the specified size and type. 
Methods inherited from class java.lang.Object 

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait 
Field Detail 

public final long nativeObj
Constructor Detail 

public Mat()
Various Mat constructors
These are various constructors that form a matrix. As noted in the "AutomaticAllocation", often the default constructor is enough, and the proper matrix will be allocated by an OpenCV function. The constructed matrix can further be assigned to another matrix or matrix expression or can be allocated with "Mat.create". In the former case, the old content is dereferenced.
public Mat(int rows, int cols, int type)
Various Mat constructors
These are various constructors that form a matrix. As noted in the "AutomaticAllocation", often the default constructor is enough, and the proper matrix will be allocated by an OpenCV function. The constructed matrix can further be assigned to another matrix or matrix expression or can be allocated with "Mat.create". In the former case, the old content is dereferenced.
rows
 Number of rows in a 2D array.cols
 Number of columns in a 2D array.type
 Array type. Use CV_8UC1,..., CV_64FC4
to create 14
channel matrices, or CV_8UC(n),..., CV_64FC(n)
to create
multichannel (up to CV_MAX_CN
channels) matrices.public Mat(int rows, int cols, int type, Scalar s)
Various Mat constructors
These are various constructors that form a matrix. As noted in the "AutomaticAllocation", often the default constructor is enough, and the proper matrix will be allocated by an OpenCV function. The constructed matrix can further be assigned to another matrix or matrix expression or can be allocated with "Mat.create". In the former case, the old content is dereferenced.
rows
 Number of rows in a 2D array.cols
 Number of columns in a 2D array.type
 Array type. Use CV_8UC1,..., CV_64FC4
to create 14
channel matrices, or CV_8UC(n),..., CV_64FC(n)
to create
multichannel (up to CV_MAX_CN
channels) matrices.s
 An optional value to initialize each matrix element with. To set all
the matrix elements to the particular value after the construction, use the
assignment operator Mat.operator=(const Scalar& value)
.public Mat(long addr)
public Mat(Mat m, Range rowRange)
Various Mat constructors
These are various constructors that form a matrix. As noted in the "AutomaticAllocation", often the default constructor is enough, and the proper matrix will be allocated by an OpenCV function. The constructed matrix can further be assigned to another matrix or matrix expression or can be allocated with "Mat.create". In the former case, the old content is dereferenced.
m
 Array that (as a whole or partly) is assigned to the constructed
matrix. No data is copied by these constructors. Instead, the header pointing
to m
data or its subarray is constructed and associated with
it. The reference counter, if any, is incremented. So, when you modify the
matrix formed using such a constructor, you also modify the corresponding
elements of m
. If you want to have an independent copy of the
subarray, use Mat.clone()
.rowRange
 Range of the m
rows to take. As usual, the range
start is inclusive and the range end is exclusive. Use Range.all()
to take all the rows.public Mat(Mat m, Range rowRange, Range colRange)
Various Mat constructors
These are various constructors that form a matrix. As noted in the "AutomaticAllocation", often the default constructor is enough, and the proper matrix will be allocated by an OpenCV function. The constructed matrix can further be assigned to another matrix or matrix expression or can be allocated with "Mat.create". In the former case, the old content is dereferenced.
m
 Array that (as a whole or partly) is assigned to the constructed
matrix. No data is copied by these constructors. Instead, the header pointing
to m
data or its subarray is constructed and associated with
it. The reference counter, if any, is incremented. So, when you modify the
matrix formed using such a constructor, you also modify the corresponding
elements of m
. If you want to have an independent copy of the
subarray, use Mat.clone()
.rowRange
 Range of the m
rows to take. As usual, the range
start is inclusive and the range end is exclusive. Use Range.all()
to take all the rows.colRange
 Range of the m
columns to take. Use
Range.all()
to take all the columns.public Mat(Mat m, Rect roi)
Various Mat constructors
These are various constructors that form a matrix. As noted in the "AutomaticAllocation", often the default constructor is enough, and the proper matrix will be allocated by an OpenCV function. The constructed matrix can further be assigned to another matrix or matrix expression or can be allocated with "Mat.create". In the former case, the old content is dereferenced.
m
 Array that (as a whole or partly) is assigned to the constructed
matrix. No data is copied by these constructors. Instead, the header pointing
to m
data or its subarray is constructed and associated with
it. The reference counter, if any, is incremented. So, when you modify the
matrix formed using such a constructor, you also modify the corresponding
elements of m
. If you want to have an independent copy of the
subarray, use Mat.clone()
.roi
 Region of interest.public Mat(Size size, int type)
Various Mat constructors
These are various constructors that form a matrix. As noted in the "AutomaticAllocation", often the default constructor is enough, and the proper matrix will be allocated by an OpenCV function. The constructed matrix can further be assigned to another matrix or matrix expression or can be allocated with "Mat.create". In the former case, the old content is dereferenced.
size
 2D array size: Size(cols, rows)
. In the
Size()
constructor, the number of rows and the number of columns
go in the reverse order.type
 Array type. Use CV_8UC1,..., CV_64FC4
to create 14
channel matrices, or CV_8UC(n),..., CV_64FC(n)
to create
multichannel (up to CV_MAX_CN
channels) matrices.public Mat(Size size, int type, Scalar s)
Various Mat constructors
These are various constructors that form a matrix. As noted in the "AutomaticAllocation", often the default constructor is enough, and the proper matrix will be allocated by an OpenCV function. The constructed matrix can further be assigned to another matrix or matrix expression or can be allocated with "Mat.create". In the former case, the old content is dereferenced.
size
 2D array size: Size(cols, rows)
. In the
Size()
constructor, the number of rows and the number of columns
go in the reverse order.type
 Array type. Use CV_8UC1,..., CV_64FC4
to create 14
channel matrices, or CV_8UC(n),..., CV_64FC(n)
to create
multichannel (up to CV_MAX_CN
channels) matrices.s
 An optional value to initialize each matrix element with. To set all
the matrix elements to the particular value after the construction, use the
assignment operator Mat.operator=(const Scalar& value)
.Method Detail 

public Mat adjustROI(int dtop, int dbottom, int dleft, int dright)
Adjusts a submatrix size and position within the parent matrix.
The method is complimentary to"Mat.locateROI". The typical use of these
functions is to determine the submatrix position within the parent matrix and
then shift the position somehow. Typically, it can be required for filtering
operations when pixels outside of the ROI should be taken into account. When
all the method parameters are positive, the ROI needs to grow in all
directions by the specified amount, for example:
// C++ code:
A.adjustROI(2, 2, 2, 2);
In this example, the matrix size is increased by 4 elements in each
direction. The matrix is shifted by 2 elements to the left and 2 elements up,
which brings in all the necessary pixels for the filtering with the 5x5
kernel.
adjustROI
forces the adjusted ROI to be inside of the parent
matrix that is boundaries of the adjusted ROI are constrained by boundaries
of the parent matrix. For example, if the submatrix A
is located
in the first row of a parent matrix and you called A.adjustROI(2, 2, 2,
2)
then A
will not be increased in the upward direction.
The function is used internally by the OpenCV filtering functions, like "filter2D", morphological operations, and so on.
dtop
 Shift of the top submatrix boundary upwards.dbottom
 Shift of the bottom submatrix boundary downwards.dleft
 Shift of the left submatrix boundary to the left.dright
 Shift of the right submatrix boundary to the right.Imgproc.copyMakeBorder(org.opencv.core.Mat, org.opencv.core.Mat, int, int, int, int, int, org.opencv.core.Scalar)
public void assignTo(Mat m)
Provides a functional form of convertTo
.
This is an internally used method called by the "MatrixExpressions" engine.
m
 Destination array.public void assignTo(Mat m, int type)
Provides a functional form of convertTo
.
This is an internally used method called by the "MatrixExpressions" engine.
m
 Destination array.type
 Desired destination array depth (or 1 if it should be the same
as the source type).public int channels()
Returns the number of matrix channels.
The method returns the number of matrix channels.
public int checkVector(int elemChannels)
public int checkVector(int elemChannels, int depth)
public int checkVector(int elemChannels, int depth, boolean requireContinuous)
public Mat clone()
Creates a full copy of the array and the underlying data.
The method creates a full copy of the array. The original step[]
is not taken into account. So, the array copy is a continuous array occupying
total()*elemSize()
bytes.
clone
in class java.lang.Object
public Mat col(int x)
Creates a matrix header for the specified matrix column.
The method makes a new header for the specified matrix column and returns it. This is an O(1) operation, regardless of the matrix size. The underlying data of the new matrix is shared with the original matrix. See also the "Mat.row" description.
x
 A 0based column index.public Mat colRange(int startcol, int endcol)
Creates a matrix header for the specified row span.
The method makes a new header for the specified column span of the matrix. Similarly to "Mat.row" and "Mat.col", this is an O(1) operation.
startcol
 An inclusive 0based start index of the column span.endcol
 An exclusive 0based ending index of the column span.public Mat colRange(Range r)
Creates a matrix header for the specified row span.
The method makes a new header for the specified column span of the matrix. Similarly to "Mat.row" and "Mat.col", this is an O(1) operation.
r
 "Range" structure containing both the start and the end indices.public int cols()
public void convertTo(Mat m, int rtype)
Converts an array to another data type with optional scaling.
The method converts source pixel values to the target data type.
saturate_cast<>
is applied at the end to avoid possible
overflows:
m(x,y) = saturate _ cast<rType>(alpha(*this)(x,y) + beta)
m
 output matrix; if it does not have a proper size or type before the
operation, it is reallocated.rtype
 desired output matrix type or, rather, the depth since the
number of channels are the same as the input has; if rtype
is
negative, the output matrix will have the same type as the input.public void convertTo(Mat m, int rtype, double alpha)
Converts an array to another data type with optional scaling.
The method converts source pixel values to the target data type.
saturate_cast<>
is applied at the end to avoid possible
overflows:
m(x,y) = saturate _ cast<rType>(alpha(*this)(x,y) + beta)
m
 output matrix; if it does not have a proper size or type before the
operation, it is reallocated.rtype
 desired output matrix type or, rather, the depth since the
number of channels are the same as the input has; if rtype
is
negative, the output matrix will have the same type as the input.alpha
 optional scale factor.public void convertTo(Mat m, int rtype, double alpha, double beta)
Converts an array to another data type with optional scaling.
The method converts source pixel values to the target data type.
saturate_cast<>
is applied at the end to avoid possible
overflows:
m(x,y) = saturate _ cast<rType>(alpha(*this)(x,y) + beta)
m
 output matrix; if it does not have a proper size or type before the
operation, it is reallocated.rtype
 desired output matrix type or, rather, the depth since the
number of channels are the same as the input has; if rtype
is
negative, the output matrix will have the same type as the input.alpha
 optional scale factor.beta
 optional delta added to the scaled values.public void copyTo(Mat m)
Copies the matrix to another one.
The method copies the matrix data to another matrix. Before copying the data,
the method invokes
// C++ code:
m.create(this>size(), this>type);
so that the destination matrix is reallocated if needed. While
m.copyTo(m);
works flawlessly, the function does not handle the
case of a partial overlap between the source and the destination matrices.
When the operation mask is specified, and the Mat.create
call
shown above reallocated the matrix, the newly allocated matrix is initialized
with all zeros before copying the data.
m
 Destination matrix. If it does not have a proper size or type before
the operation, it is reallocated.public void copyTo(Mat m, Mat mask)
Copies the matrix to another one.
The method copies the matrix data to another matrix. Before copying the data,
the method invokes
// C++ code:
m.create(this>size(), this>type);
so that the destination matrix is reallocated if needed. While
m.copyTo(m);
works flawlessly, the function does not handle the
case of a partial overlap between the source and the destination matrices.
When the operation mask is specified, and the Mat.create
call
shown above reallocated the matrix, the newly allocated matrix is initialized
with all zeros before copying the data.
m
 Destination matrix. If it does not have a proper size or type before
the operation, it is reallocated.mask
 Operation mask. Its nonzero elements indicate which matrix
elements need to be copied.public void create(int rows, int cols, int type)
Allocates new array data if needed.
This is one of the key Mat
methods. Most newstyle OpenCV
functions and methods that produce arrays call this method for each output
array. The method uses the following algorithm:
total()*elemSize()
bytes.
Such a scheme makes the memory management robust and efficient at the same
time and helps avoid extra typing for you. This means that usually there is
no need to explicitly allocate output arrays. That is, instead of writing:
// C++ code:
Mat color;...
Mat gray(color.rows, color.cols, color.depth());
cvtColor(color, gray, CV_BGR2GRAY);
you can simply write:
Mat color;...
Mat gray;
cvtColor(color, gray, CV_BGR2GRAY);
because
cvtColor
, as well as the most of OpenCV functions, calls
Mat.create()
for the output array internally.
rows
 New number of rows.cols
 New number of columns.type
 New matrix type.public void create(Size size, int type)
Allocates new array data if needed.
This is one of the key Mat
methods. Most newstyle OpenCV
functions and methods that produce arrays call this method for each output
array. The method uses the following algorithm:
total()*elemSize()
bytes.
Such a scheme makes the memory management robust and efficient at the same
time and helps avoid extra typing for you. This means that usually there is
no need to explicitly allocate output arrays. That is, instead of writing:
// C++ code:
Mat color;...
Mat gray(color.rows, color.cols, color.depth());
cvtColor(color, gray, CV_BGR2GRAY);
you can simply write:
Mat color;...
Mat gray;
cvtColor(color, gray, CV_BGR2GRAY);
because
cvtColor
, as well as the most of OpenCV functions, calls
Mat.create()
for the output array internally.
size
 Alternative new matrix size specification: Size(cols,
rows)
type
 New matrix type.public Mat cross(Mat m)
Computes a crossproduct of two 3element vectors.
The method computes a crossproduct of two 3element vectors. The vectors must be 3element floatingpoint vectors of the same shape and size. The result is another 3element vector of the same shape and type as operands.
m
 Another crossproduct operand.public long dataAddr()
public int depth()
Returns the depth of a matrix element.
The method returns the identifier of the matrix element depth (the type of
each individual channel). For example, for a 16bit signed 3channel array,
the method returns CV_16S
. A complete list of matrix types
contains the following values:
CV_8U
 8bit unsigned integers (0..255
)
CV_8S
 8bit signed integers (128..127
)
CV_16U
 16bit unsigned integers (0..65535
)
CV_16S
 16bit signed integers (32768..32767
)
CV_32S
 32bit signed integers (2147483648..2147483647
)
CV_32F
 32bit floatingpoint numbers (FLT_MAX..FLT_MAX,
INF, NAN
)
CV_64F
 64bit floatingpoint numbers (DBL_MAX..DBL_MAX,
INF, NAN
)
public Mat diag()
Extracts a diagonal from a matrix, or creates a diagonal matrix.
The method makes a new header for the specified matrix diagonal. The new matrix is represented as a singlecolumn matrix. Similarly to "Mat.row" and "Mat.col", this is an O(1) operation.
public Mat diag(int d)
Extracts a diagonal from a matrix, or creates a diagonal matrix.
The method makes a new header for the specified matrix diagonal. The new matrix is represented as a singlecolumn matrix. Similarly to "Mat.row" and "Mat.col", this is an O(1) operation.
d
 Singlecolumn matrix that forms a diagonal matrix or index of the
diagonal, with the following values:
d=1
means the diagonal is set immediately below the main one.
d=1
means the diagonal is set immediately above the main one.
public static Mat diag(Mat d)
Extracts a diagonal from a matrix, or creates a diagonal matrix.
The method makes a new header for the specified matrix diagonal. The new matrix is represented as a singlecolumn matrix. Similarly to "Mat.row" and "Mat.col", this is an O(1) operation.
d
 Singlecolumn matrix that forms a diagonal matrix or index of the
diagonal, with the following values:
d=1
means the diagonal is set immediately below the main one.
d=1
means the diagonal is set immediately above the main one.
public double dot(Mat m)
Computes a dotproduct of two vectors.
The method computes a dotproduct of two matrices. If the matrices are not singlecolumn or singlerow vectors, the toptobottom lefttoright scan ordering is used to treat them as 1D vectors. The vectors must have the same size and type. If the matrices have more than one channel, the dot products from all the channels are summed together.
m
 another dotproduct operand.public java.lang.String dump()
public long elemSize()
Returns the matrix element size in bytes.
The method returns the matrix element size in bytes. For example, if the
matrix type is CV_16SC3
, the method returns 3*sizeof(short)
or 6.
public long elemSize1()
Returns the size of each matrix element channel in bytes.
The method returns the matrix element channel size in bytes, that is, it
ignores the number of channels. For example, if the matrix type is
CV_16SC3
, the method returns sizeof(short)
or 2.
public boolean empty()
Returns true
if the array has no elements.
The method returns true
if Mat.total()
is 0 or if
Mat.data
is NULL. Because of pop_back()
and
resize()
methods M.total() == 0
does not imply that
M.data == NULL
.
public static Mat eye(int rows, int cols, int type)
Returns an identity matrix of the specified size and type.
The method returns a Matlabstyle identity matrix initializer, similarly to
"Mat.zeros". Similarly to"Mat.ones", you can use a scale operation to
create a scaled identity matrix efficiently:
// C++ code:
// make a 4x4 diagonal matrix with 0.1's on the diagonal.
Mat A = Mat.eye(4, 4, CV_32F)*0.1;
 Parameters:
rows
 Number of rows.cols
 Number of columns.type
 Created matrix type. See Also:
 org.opencv.core.Mat.eye
eye
public static Mat eye(Size size,
int type)
Returns an identity matrix of the specified size and type.
The method returns a Matlabstyle identity matrix initializer, similarly to
"Mat.zeros". Similarly to"Mat.ones", you can use a scale operation to
create a scaled identity matrix efficiently:
// C++ code:
// make a 4x4 diagonal matrix with 0.1's on the diagonal.
Mat A = Mat.eye(4, 4, CV_32F)*0.1;
 Parameters:
size
 Alternative matrix size specification as Size(cols,
rows)
.type
 Created matrix type. See Also:
 org.opencv.core.Mat.eye
finalize
protected void finalize()
throws java.lang.Throwable
 Overrides:
finalize
in class java.lang.Object
 Throws:
java.lang.Throwable
get
public double[] get(int row,
int col)
get
public int get(int row,
int col,
byte[] data)
get
public int get(int row,
int col,
double[] data)
get
public int get(int row,
int col,
float[] data)
get
public int get(int row,
int col,
int[] data)
get
public int get(int row,
int col,
short[] data)
getNativeObjAddr
public long getNativeObjAddr()
height
public int height()
inv
public Mat inv()
Inverses a matrix.
The method performs a matrix inversion by means of matrix expressions. This
means that a temporary matrix inversion object is returned by the method and
can be used further as a part of more complex matrix expressions or can be
assigned to a matrix.
 See Also:
 org.opencv.core.Mat.inv
inv
public Mat inv(int method)
Inverses a matrix.
The method performs a matrix inversion by means of matrix expressions. This
means that a temporary matrix inversion object is returned by the method and
can be used further as a part of more complex matrix expressions or can be
assigned to a matrix.
 Parameters:
method
 Matrix inversion method. Possible values are the following:
 DECOMP_LU is the LU decomposition. The matrix must be nonsingular.
 DECOMP_CHOLESKY is the Cholesky LL^T decomposition for
symmetrical positively defined matrices only. This type is about twice faster
than LU on big matrices.
 DECOMP_SVD is the SVD decomposition. If the matrix is singular or even
nonsquare, the pseudo inversion is computed.
 See Also:
 org.opencv.core.Mat.inv
isContinuous
public boolean isContinuous()
Reports whether the matrix is continuous or not.
The method returns true
if the matrix elements are stored
continuously without gaps at the end of each row. Otherwise, it returns
false
. Obviously, 1x1
or 1xN
matrices
are always continuous. Matrices created with "Mat.create" are always
continuous. But if you extract a part of the matrix using "Mat.col",
"Mat.diag", and so on, or constructed a matrix header for externally
allocated data, such matrices may no longer have this property.
The continuity flag is stored as a bit in the Mat.flags
field
and is computed automatically when you construct a matrix header. Thus, the
continuity check is a very fast operation, though theoretically it could be
done as follows:
// C++ code:
// alternative implementation of Mat.isContinuous()
bool myCheckMatContinuity(const Mat& m)
//return (m.flags & Mat.CONTINUOUS_FLAG) != 0;
return m.rows == 1  m.step == m.cols*m.elemSize();
The method is used in quite a few of OpenCV functions. The point is that
elementwise operations (such as arithmetic and logical operations, math
functions, alpha blending, color space transformations, and others) do not
depend on the image geometry. Thus, if all the input and output arrays are
continuous, the functions can process them as very long singlerow vectors.
The example below illustrates how an alphablending function can be
implemented.
template
void alphaBlendRGBA(const Mat& src1, const Mat& src2, Mat& dst)
const float alpha_scale = (float)std.numeric_limits.max(),
inv_scale = 1.f/alpha_scale;
CV_Assert(src1.type() == src2.type() &&
src1.type() == CV_MAKETYPE(DataType.depth, 4) &&
src1.size() == src2.size());
Size size = src1.size();
dst.create(size, src1.type());
// here is the idiom: check the arrays for continuity and,
// if this is the case,
// treat the arrays as 1D vectors
if(src1.isContinuous() && src2.isContinuous() && dst.isContinuous())
size.width *= size.height;
size.height = 1;
size.width *= 4;
for(int i = 0; i < size.height; i++)
// when the arrays are continuous,
// the outer loop is executed only once
const T* ptr1 = src1.ptr(i);
const T* ptr2 = src2.ptr(i);
T* dptr = dst.ptr(i);
for(int j = 0; j < size.width; j += 4)
float alpha = ptr1[j+3]*inv_scale, beta = ptr2[j+3]*inv_scale;
dptr[j] = saturate_cast(ptr1[j]*alpha + ptr2[j]*beta);
dptr[j+1] = saturate_cast(ptr1[j+1]*alpha + ptr2[j+1]*beta);
dptr[j+2] = saturate_cast(ptr1[j+2]*alpha + ptr2[j+2]*beta);
dptr[j+3] = saturate_cast((1  (1alpha)*(1beta))*alpha_scale);
This approach, while being very simple, can boost the performance of a simple
elementoperation by 1020 percents, especially if the image is rather small
and the operation is quite simple.
Another OpenCV idiom in this function, a call of "Mat.create" for the
destination array, that allocates the destination array unless it already has
the proper size and type. And while the newly allocated arrays are always
continuous, you still need to check the destination array because
"Mat.create" does not always allocate a new matrix.
 See Also:
 org.opencv.core.Mat.isContinuous
isSubmatrix
public boolean isSubmatrix()
locateROI
public void locateROI(Size wholeSize,
Point ofs)
Locates the matrix header within a parent matrix.
After you extracted a submatrix from a matrix using "Mat.row", "Mat.col",
"Mat.rowRange", "Mat.colRange", and others, the resultant submatrix points
just to the part of the original big matrix. However, each submatrix contains
information (represented by datastart
and dataend
fields) that helps reconstruct the original matrix size and the position of
the extracted submatrix within the original matrix. The method
locateROI
does exactly that.
 Parameters:
wholeSize
 Output parameter that contains the size of the whole matrix
containing *this
as a part.ofs
 Output parameter that contains an offset of *this
inside the whole matrix. See Also:
 org.opencv.core.Mat.locateROI
mul
public Mat mul(Mat m)
Performs an elementwise multiplication or division of the two matrices.
The method returns a temporary object encoding perelement array
multiplication, with optional scale. Note that this is not a matrix
multiplication that corresponds to a simpler "*" operator.
Example:
// C++ code:
Mat C = A.mul(5/B); // equivalent to divide(A, B, C, 5)
 Parameters:
m
 Another array of the same type and the same size as
*this
, or a matrix expression. See Also:
 org.opencv.core.Mat.mul
mul
public Mat mul(Mat m,
double scale)
Performs an elementwise multiplication or division of the two matrices.
The method returns a temporary object encoding perelement array
multiplication, with optional scale. Note that this is not a matrix
multiplication that corresponds to a simpler "*" operator.
Example:
// C++ code:
Mat C = A.mul(5/B); // equivalent to divide(A, B, C, 5)
 Parameters:
m
 Another array of the same type and the same size as
*this
, or a matrix expression.scale
 Optional scale factor. See Also:
 org.opencv.core.Mat.mul
ones
public static Mat ones(int rows,
int cols,
int type)
Returns an array of all 1's of the specified size and type.
The method returns a Matlabstyle 1's array initializer, similarly
to"Mat.zeros". Note that using this method you can initialize an array with
an arbitrary value, using the following Matlab idiom:
// C++ code:
Mat A = Mat.ones(100, 100, CV_8U)*3; // make 100x100 matrix filled with 3.
The above operation does not form a 100x100 matrix of 1's and then multiply
it by 3. Instead, it just remembers the scale factor (3 in this case) and use
it when actually invoking the matrix initializer.
 Parameters:
rows
 Number of rows.cols
 Number of columns.type
 Created matrix type. See Also:
 org.opencv.core.Mat.ones
ones
public static Mat ones(Size size,
int type)
Returns an array of all 1's of the specified size and type.
The method returns a Matlabstyle 1's array initializer, similarly
to"Mat.zeros". Note that using this method you can initialize an array with
an arbitrary value, using the following Matlab idiom:
// C++ code:
Mat A = Mat.ones(100, 100, CV_8U)*3; // make 100x100 matrix filled with 3.
The above operation does not form a 100x100 matrix of 1's and then multiply
it by 3. Instead, it just remembers the scale factor (3 in this case) and use
it when actually invoking the matrix initializer.
 Parameters:
size
 Alternative to the matrix size specification Size(cols,
rows)
.type
 Created matrix type. See Also:
 org.opencv.core.Mat.ones
push_back
public void push_back(Mat m)
Adds elements to the bottom of the matrix.
The methods add one or more elements to the bottom of the matrix. They
emulate the corresponding method of the STL vector class. When
elem
is Mat
, its type and the number of columns
must be the same as in the container matrix.
 Parameters:
m
 a m See Also:
 org.opencv.core.Mat.push_back
put
public int put(int row,
int col,
byte[] data)
put
public int put(int row,
int col,
double... data)
put
public int put(int row,
int col,
float[] data)
put
public int put(int row,
int col,
int[] data)
put
public int put(int row,
int col,
short[] data)
release
public void release()
Decrements the reference counter and deallocates the matrix if needed.
The method decrements the reference counter associated with the matrix data.
When the reference counter reaches 0, the matrix data is deallocated and the
data and the reference counter pointers are set to NULL's. If the matrix
header points to an external data set (see "Mat.Mat"), the reference counter
is NULL, and the method has no effect in this case.
This method can be called manually to force the matrix data deallocation. But
since this method is automatically called in the destructor, or by any other
method that changes the data pointer, it is usually not needed. The reference
counter decrement and check for 0 is an atomic operation on the platforms
that support it. Thus, it is safe to operate on the same matrices
asynchronously in different threads.
 See Also:
 org.opencv.core.Mat.release
reshape
public Mat reshape(int cn)
Changes the shape and/or the number of channels of a 2D matrix without
copying the data.
The method makes a new matrix header for *this
elements. The new
matrix may have a different size and/or different number of channels. Any
combination is possible if:
 No extra elements are included into the new matrix and no elements are
excluded. Consequently, the product
rows*cols*channels()
must
stay the same after the transformation.
 No data is copied. That is, this is an O(1) operation. Consequently,
if you change the number of rows, or the operation changes the indices of
elements row in some other way, the matrix must be continuous. See
"Mat.isContinuous".
For example, if there is a set of 3D points stored as an STL vector, and you
want to represent the points as a 3xN
matrix, do the following:
// C++ code:
std.vector vec;...
Mat pointMat = Mat(vec). // convert vector to Mat, O(1) operation
reshape(1). // make Nx3 1channel matrix out of Nx1 3channel.
// Also, an O(1) operation
t(); // finally, transpose the Nx3 matrix.
// This involves copying all the elements
 Parameters:
cn
 New number of channels. If the parameter is 0, the number of
channels remains the same. See Also:
 org.opencv.core.Mat.reshape
reshape
public Mat reshape(int cn,
int rows)
Changes the shape and/or the number of channels of a 2D matrix without
copying the data.
The method makes a new matrix header for *this
elements. The new
matrix may have a different size and/or different number of channels. Any
combination is possible if:
 No extra elements are included into the new matrix and no elements are
excluded. Consequently, the product
rows*cols*channels()
must
stay the same after the transformation.
 No data is copied. That is, this is an O(1) operation. Consequently,
if you change the number of rows, or the operation changes the indices of
elements row in some other way, the matrix must be continuous. See
"Mat.isContinuous".
For example, if there is a set of 3D points stored as an STL vector, and you
want to represent the points as a 3xN
matrix, do the following:
// C++ code:
std.vector vec;...
Mat pointMat = Mat(vec). // convert vector to Mat, O(1) operation
reshape(1). // make Nx3 1channel matrix out of Nx1 3channel.
// Also, an O(1) operation
t(); // finally, transpose the Nx3 matrix.
// This involves copying all the elements
 Parameters:
cn
 New number of channels. If the parameter is 0, the number of
channels remains the same.rows
 New number of rows. If the parameter is 0, the number of rows
remains the same. See Also:
 org.opencv.core.Mat.reshape
row
public Mat row(int y)
Creates a matrix header for the specified matrix row.
The method makes a new header for the specified matrix row and returns it.
This is an O(1) operation, regardless of the matrix size. The underlying data
of the new matrix is shared with the original matrix. Here is the example of
one of the classical basic matrix processing operations, axpy
,
used by LU and many other algorithms:
// C++ code:
inline void matrix_axpy(Mat& A, int i, int j, double alpha)
A.row(i) += A.row(j)*alpha;
Note:
In the current implementation, the following code does not work as expected:
// C++ code:
Mat A;...
A.row(i) = A.row(j); // will not work
This happens because A.row(i)
forms a temporary header that is
further assigned to another header. Remember that each of these operations is
O(1), that is, no data is copied. Thus, the above assignment is not true if
you may have expected the jth row to be copied to the ith row. To achieve
that, you should either turn this simple assignment into an expression or use
the "Mat.copyTo" method:
Mat A;...
// works, but looks a bit obscure.
A.row(i) = A.row(j) + 0;
// this is a bit longer, but the recommended method.
A.row(j).copyTo(A.row(i));
 Parameters:
y
 A 0based row index. See Also:
 org.opencv.core.Mat.row
rowRange
public Mat rowRange(int startrow,
int endrow)
Creates a matrix header for the specified row span.
The method makes a new header for the specified row span of the matrix.
Similarly to "Mat.row" and "Mat.col", this is an O(1) operation.
 Parameters:
startrow
 An inclusive 0based start index of the row span.endrow
 An exclusive 0based ending index of the row span. See Also:
 org.opencv.core.Mat.rowRange
rowRange
public Mat rowRange(Range r)
Creates a matrix header for the specified row span.
The method makes a new header for the specified row span of the matrix.
Similarly to "Mat.row" and "Mat.col", this is an O(1) operation.
 Parameters:
r
 "Range" structure containing both the start and the end indices. See Also:
 org.opencv.core.Mat.rowRange
rows
public int rows()
setTo
public Mat setTo(Mat value)
Sets all or some of the array elements to the specified value.
 Parameters:
value
 Assigned scalar converted to the actual array type. See Also:
 org.opencv.core.Mat.setTo
setTo
public Mat setTo(Mat value,
Mat mask)
Sets all or some of the array elements to the specified value.
 Parameters:
value
 Assigned scalar converted to the actual array type.mask
 Operation mask of the same size as *this
. This is an
advanced variant of the Mat.operator=(const Scalar& s)
operator. See Also:
 org.opencv.core.Mat.setTo
setTo
public Mat setTo(Scalar s)
setTo
public Mat setTo(Scalar value,
Mat mask)
Sets all or some of the array elements to the specified value.
 Parameters:
value
 Assigned scalar converted to the actual array type.mask
 Operation mask of the same size as *this
. This is an
advanced variant of the Mat.operator=(const Scalar& s)
operator. See Also:
 org.opencv.core.Mat.setTo
size
public Size size()
Returns a matrix size.
The method returns a matrix size: Size(cols, rows)
. When the
matrix is more than 2dimensional, the returned size is (1, 1).
 See Also:
 org.opencv.core.Mat.size
step1
public long step1()
Returns a normalized step.
The method returns a matrix step divided by "Mat.elemSize1()". It can be
useful to quickly access an arbitrary matrix element.
 See Also:
 org.opencv.core.Mat.step1
step1
public long step1(int i)
Returns a normalized step.
The method returns a matrix step divided by "Mat.elemSize1()". It can be
useful to quickly access an arbitrary matrix element.
 Parameters:
i
 a i See Also:
 org.opencv.core.Mat.step1
submat
public Mat submat(int rowStart,
int rowEnd,
int colStart,
int colEnd)
Extracts a rectangular submatrix.
The operators make a new header for the specified subarray of
*this
. They are the most generalized forms of "Mat.row",
"Mat.col", "Mat.rowRange", and "Mat.colRange". For example,
A(Range(0, 10), Range.all())
is equivalent to A.rowRange(0,
10)
. Similarly to all of the above, the operators are O(1) operations,
that is, no matrix data is copied.
 Parameters:
rowStart
 a rowStartrowEnd
 a rowEndcolStart
 a colStartcolEnd
 a colEnd See Also:
 org.opencv.core.Mat.operator()
submat
public Mat submat(Range rowRange,
Range colRange)
Extracts a rectangular submatrix.
The operators make a new header for the specified subarray of
*this
. They are the most generalized forms of "Mat.row",
"Mat.col", "Mat.rowRange", and "Mat.colRange". For example,
A(Range(0, 10), Range.all())
is equivalent to A.rowRange(0,
10)
. Similarly to all of the above, the operators are O(1) operations,
that is, no matrix data is copied.
 Parameters:
rowRange
 Start and end row of the extracted submatrix. The upper
boundary is not included. To select all the rows, use Range.all()
.colRange
 Start and end column of the extracted submatrix. The upper
boundary is not included. To select all the columns, use Range.all()
. See Also:
 org.opencv.core.Mat.operator()
submat
public Mat submat(Rect roi)
Extracts a rectangular submatrix.
The operators make a new header for the specified subarray of
*this
. They are the most generalized forms of "Mat.row",
"Mat.col", "Mat.rowRange", and "Mat.colRange". For example,
A(Range(0, 10), Range.all())
is equivalent to A.rowRange(0,
10)
. Similarly to all of the above, the operators are O(1) operations,
that is, no matrix data is copied.
 Parameters:
roi
 Extracted submatrix specified as a rectangle. See Also:
 org.opencv.core.Mat.operator()
t
public Mat t()
Transposes a matrix.
The method performs matrix transposition by means of matrix expressions. It
does not perform the actual transposition but returns a temporary matrix
transposition object that can be further used as a part of more complex
matrix expressions or can be assigned to a matrix:
// C++ code:
Mat A1 = A + Mat.eye(A.size(), A.type)*lambda;
Mat C = A1.t()*A1; // compute (A + lambda*I)^t * (A + lamda*I)
 See Also:
 org.opencv.core.Mat.t
toString
public java.lang.String toString()
 Overrides:
toString
in class java.lang.Object
total
public long total()
Returns the total number of array elements.
The method returns the number of array elements (a number of pixels if the
array represents an image).
 See Also:
 org.opencv.core.Mat.total
type
public int type()
Returns the type of a matrix element.
The method returns a matrix element type. This is an identifier compatible
with the CvMat
type system, like CV_16SC3
or 16bit
signed 3channel array, and so on.
 See Also:
 org.opencv.core.Mat.type
width
public int width()
zeros
public static Mat zeros(int rows,
int cols,
int type)
Returns a zero array of the specified size and type.
The method returns a Matlabstyle zero array initializer. It can be used to
quickly form a constant array as a function parameter, part of a matrix
expression, or as a matrix initializer.
// C++ code:
Mat A;
A = Mat.zeros(3, 3, CV_32F);
In the example above, a new matrix is allocated only if A
is not
a 3x3 floatingpoint matrix. Otherwise, the existing matrix A
is
filled with zeros.
 Parameters:
rows
 Number of rows.cols
 Number of columns.type
 Created matrix type. See Also:
 org.opencv.core.Mat.zeros
zeros
public static Mat zeros(Size size,
int type)
Returns a zero array of the specified size and type.
The method returns a Matlabstyle zero array initializer. It can be used to
quickly form a constant array as a function parameter, part of a matrix
expression, or as a matrix initializer.
// C++ code:
Mat A;
A = Mat.zeros(3, 3, CV_32F);
In the example above, a new matrix is allocated only if A
is not
a 3x3 floatingpoint matrix. Otherwise, the existing matrix A
is
filled with zeros.
 Parameters:
size
 Alternative to the matrix size specification Size(cols,
rows)
.type
 Created matrix type. See Also:
 org.opencv.core.Mat.zeros
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