Matrix Reductions

gpu::meanStdDev

Computes a mean value and a standard deviation of matrix elements.

C++: void gpu::meanStdDev(const GpuMat& mtx, Scalar& mean, Scalar& stddev)

C++: void gpu::meanStdDev(const GpuMat& mtx, Scalar& mean, Scalar& stddev, GpuMat& buf)

Parameters:

• mtx – Source matrix. CV_8UC1 matrices are supported for now.
• mean – Mean value.
• stddev – Standard deviation value.
• buf – Optional buffer to avoid extra memory allocations. It is resized automatically.

See also

meanStdDev()

gpu::norm

Returns the norm of a matrix (or difference of two matrices).

C++: double gpu::norm(const GpuMat& src1, int normType=NORM_L2)

C++: double gpu::norm(const GpuMat& src1, int normType, GpuMat& buf)

C++: double gpu::norm(const GpuMat& src1, const GpuMat& src2, int normType=NORM_L2)

Parameters:

• src1 – Source matrix. Any matrices except 64F are supported.
• src2 – Second source matrix (if any) with the same size and type as src1.
• normType – Norm type. NORM_L1 , NORM_L2 , and NORM_INF are supported for now.
• buf – Optional buffer to avoid extra memory allocations. It is resized automatically.

See also

norm()

gpu::sum

Returns the sum of matrix elements.

C++: Scalar gpu::sum(const GpuMat& src)

C++: Scalar gpu::sum(const GpuMat& src, GpuMat& buf)

Parameters:

• src – Source image of any depth except for CV_64F .
• buf – Optional buffer to avoid extra memory allocations. It is resized automatically.

See also

sum()

gpu::absSum

Returns the sum of absolute values for matrix elements.

C++: Scalar gpu::absSum(const GpuMat& src)

C++: Scalar gpu::absSum(const GpuMat& src, GpuMat& buf)

Parameters:

• src – Source image of any depth except for CV_64F .
• buf – Optional buffer to avoid extra memory allocations. It is resized automatically.

gpu::sqrSum

Returns the squared sum of matrix elements.

C++: Scalar gpu::sqrSum(const GpuMat& src)

C++: Scalar gpu::sqrSum(const GpuMat& src, GpuMat& buf)

Parameters:

• src – Source image of any depth except for CV_64F .
• buf – Optional buffer to avoid extra memory allocations. It is resized automatically.

gpu::minMax

Finds global minimum and maximum matrix elements and returns their values.

C++: void gpu::minMax(const GpuMat& src, double* minVal, double* maxVal=0, const GpuMat& mask=GpuMat())

C++: void gpu::minMax(const GpuMat& src, double* minVal, double* maxVal, const GpuMat& mask, GpuMat& buf)

Parameters:

• src – Single-channel source image.
• minVal – Pointer to the returned minimum value. Use NULL if not required.
• maxVal – Pointer to the returned maximum value. Use NULL if not required.
• mask – Optional mask to select a sub-matrix.
• buf – Optional buffer to avoid extra memory allocations. It is resized automatically.

The function does not work with CV_64F images on GPUs with the compute capability < 1.3.

See also

minMaxLoc()

gpu::minMaxLoc

Finds global minimum and maximum matrix elements and returns their values with locations.

C++: void gpu::minMaxLoc(const GpuMat& src, double* minVal, double* maxVal=0, Point* minLoc=0, Point* maxLoc=0, const GpuMat& mask=GpuMat())

C++: void gpu::minMaxLoc(const GpuMat& src, double* minVal, double* maxVal, Point* minLoc, Point* maxLoc, const GpuMat& mask, GpuMat& valbuf, GpuMat& locbuf)

Parameters:

• src – Single-channel source image.
• minVal – Pointer to the returned minimum value. Use NULL if not required.
• maxVal – Pointer to the returned maximum value. Use NULL if not required.
• minLoc – Pointer to the returned minimum location. Use NULL if not required.
• maxLoc – Pointer to the returned maximum location. Use NULL if not required.
• mask – Optional mask to select a sub-matrix.
• valbuf – Optional values buffer to avoid extra memory allocations. It is resized automatically.
• locbuf – Optional locations buffer to avoid extra memory allocations. It is resized automatically.

The function does not work with CV_64F images on GPU with the compute capability < 1.3.

See also

minMaxLoc()

gpu::countNonZero

Counts non-zero matrix elements.

C++: int gpu::countNonZero(const GpuMat& src)

C++: int gpu::countNonZero(const GpuMat& src, GpuMat& buf)

Parameters:

• src – Single-channel source image.
• buf – Optional buffer to avoid extra memory allocations. It is resized automatically.

The function does not work with CV_64F images on GPUs with the compute capability < 1.3.

See also

countNonZero()

gpu::reduce

Reduces a matrix to a vector.

C++: void gpu::reduce(const GpuMat& mtx, GpuMat& vec, int dim, int reduceOp, int dtype=-1, Stream& stream=Stream::Null())

Parameters:

• mtx – Source 2D matrix.
• vec – Destination vector. Its size and type is defined by dim and dtype parameters.
• dim – Dimension index along which the matrix is reduced. 0 means that the matrix is reduced to a single row. 1 means that the matrix is reduced to a single column.
• reduceOp –

  Reduction operation that could be one of the following:

  • CV_REDUCE_SUM The output is the sum of all rows/columns of the matrix.
  • CV_REDUCE_AVG The output is the mean vector of all rows/columns of the matrix.
  • CV_REDUCE_MAX The output is the maximum (column/row-wise) of all rows/columns of the matrix.
  • CV_REDUCE_MIN The output is the minimum (column/row-wise) of all rows/columns of the matrix.
• dtype – When it is negative, the destination vector will have the same type as the source matrix. Otherwise, its type will be CV_MAKE_TYPE(CV_MAT_DEPTH(dtype), mtx.channels()) .

The function reduce reduces the matrix to a vector by treating the matrix rows/columns as a set of 1D vectors and performing the specified operation on the vectors until a single row/column is obtained. For example, the function can be used to compute horizontal and vertical projections of a raster image. In case of CV_REDUCE_SUM and CV_REDUCE_AVG , the output may have a larger element bit-depth to preserve accuracy. And multi-channel arrays are also supported in these two reduction modes.

See also

reduce()