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# Image Filtering

Functions and classes described in this section are used to perform various linear or non-linear filtering operations on 2D images.

## gpu::BaseRowFilter_GPU

class `gpu::``BaseRowFilter_GPU`

Base class for linear or non-linear filters that processes rows of 2D arrays. Such filters are used for the “horizontal” filtering passes in separable filters.

    class BaseRowFilter_GPU
    {
    public:
        BaseRowFilter_GPU(int ksize_, int anchor_);
        virtual ~BaseRowFilter_GPU() {}
        virtual void operator()(const GpuMat& src, GpuMat& dst, Stream& stream = Stream::Null()) = 0;
        int ksize, anchor;
    };

Note

This class does not allocate memory for a destination image. Usually this class is used inside `gpu::FilterEngine_GPU`.

## gpu::BaseColumnFilter_GPU

class `gpu::``BaseColumnFilter_GPU`

Base class for linear or non-linear filters that processes columns of 2D arrays. Such filters are used for the “vertical” filtering passes in separable filters.

    class BaseColumnFilter_GPU
    {
    public:
        BaseColumnFilter_GPU(int ksize_, int anchor_);
        virtual ~BaseColumnFilter_GPU() {}
        virtual void operator()(const GpuMat& src, GpuMat& dst, Stream& stream = Stream::Null()) = 0;
        int ksize, anchor;
    };

Note

This class does not allocate memory for a destination image. Usually this class is used inside `gpu::FilterEngine_GPU`.

## gpu::BaseFilter_GPU

class `gpu::``BaseFilter_GPU`

Base class for non-separable 2D filters.

    class CV_EXPORTS BaseFilter_GPU
    {
    public:
        BaseFilter_GPU(const Size& ksize_, const Point& anchor_);
        virtual ~BaseFilter_GPU() {}
        virtual void operator()(const GpuMat& src, GpuMat& dst, Stream& stream = Stream::Null()) = 0;
        Size ksize;
        Point anchor;
    };

Note

This class does not allocate memory for a destination image. Usually this class is used inside `gpu::FilterEngine_GPU`.

## gpu::FilterEngine_GPU

class `gpu::``FilterEngine_GPU`

Base class for the Filter Engine.

    class CV_EXPORTS FilterEngine_GPU
    {
    public:
        virtual ~FilterEngine_GPU() {}

        virtual void apply(const GpuMat& src, GpuMat& dst,
                           Rect roi = Rect(0,0,-1,-1), Stream& stream = Stream::Null()) = 0;
    };

The class can be used to apply an arbitrary filtering operation to an image. It contains all the necessary intermediate buffers. Pointers to the initialized `FilterEngine_GPU` instances are returned by various `create*Filter_GPU` functions (see below), and they are used inside high-level functions such as `gpu::filter2D()`, `gpu::erode()`, `gpu::Sobel()` , and others.

By using `FilterEngine_GPU` instead of functions you can avoid unnecessary memory allocation for intermediate buffers and get better performance:

    while (...)
    {
        gpu::GpuMat src = getImg();
        gpu::GpuMat dst;
        // Allocate and release buffers at each iterations
        gpu::GaussianBlur(src, dst, ksize, sigma1);
    }

    // Allocate buffers only once
    cv::Ptr<gpu::FilterEngine_GPU> filter =
        gpu::createGaussianFilter_GPU(CV_8UC4, ksize, sigma1);
    while (...)
    {
        gpu::GpuMat src = getImg();
        gpu::GpuMat dst;
        filter->apply(src, dst, cv::Rect(0, 0, src.cols, src.rows));
    }
    // Release buffers only once
    filter.release();

`FilterEngine_GPU` can process a rectangular sub-region of an image. By default, if `roi == Rect(0,0,-1,-1)` , `FilterEngine_GPU` processes the inner region of an image ( `Rect(anchor.x, anchor.y, src_size.width - ksize.width, src_size.height - ksize.height)` ) because some filters do not check whether indices are outside the image for better performance. See below to understand which filters support processing the whole image and which do not and identify image type limitations.

Note

The GPU filters do not support the in-place mode.

See also

`gpu::BaseRowFilter_GPU`, `gpu::BaseColumnFilter_GPU`, `gpu::BaseFilter_GPU`, `gpu::createFilter2D_GPU()`, `gpu::createSeparableFilter_GPU()`, `gpu::createBoxFilter_GPU()`, `gpu::createMorphologyFilter_GPU()`, `gpu::createLinearFilter_GPU()`, `gpu::createSeparableLinearFilter_GPU()`, `gpu::createDerivFilter_GPU()`, `gpu::createGaussianFilter_GPU()`

## gpu::createFilter2D_GPU

Creates a non-separable filter engine with the specified filter.

C++:`` Ptr<FilterEngine_GPU> `gpu::``createFilter2D_GPU`(const Ptr<BaseFilter_GPU>& filter2D, int srcType, int dstType)

  Parameters:

  - filter2D – Non-separable 2D filter.
  - srcType – Input image type. It must be supported by `filter2D` .
  - dstType – Output image type. It must be supported by `filter2D` .

Usually this function is used inside such high-level functions as `gpu::createLinearFilter_GPU()`, `gpu::createBoxFilter_GPU()`.

## gpu::createSeparableFilter_GPU

Creates a separable filter engine with the specified filters.

C++:`` Ptr<FilterEngine_GPU> `gpu::``createSeparableFilter_GPU`(const Ptr<BaseRowFilter_GPU>& rowFilter, const Ptr<BaseColumnFilter_GPU>& columnFilter, int srcType, int bufType, int dstType)

  Parameters:

  - rowFilter – “Horizontal” 1D filter.
  - columnFilter – “Vertical” 1D filter.
  - srcType – Input image type. It must be supported by `rowFilter` .
  - bufType – Buffer image type. It must be supported by `rowFilter` and `columnFilter` .
  - dstType – Output image type. It must be supported by `columnFilter` .

Usually this function is used inside such high-level functions as `gpu::createSeparableLinearFilter_GPU()`.

## gpu::getRowSumFilter_GPU

Creates a horizontal 1D box filter.

C++:`` Ptr<BaseRowFilter_GPU> `gpu::``getRowSumFilter_GPU`(int srcType, int sumType, int ksize, int anchor=-1)

  Parameters:

  - srcType – Input image type. Only `CV_8UC1` type is supported for now.
  - sumType – Output image type. Only `CV_32FC1` type is supported for now.
  - ksize – Kernel size.
  - anchor – Anchor point. The default value (-1) means that the anchor is at the kernel center.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

## gpu::getColumnSumFilter_GPU

Creates a vertical 1D box filter.

C++:`` Ptr<BaseColumnFilter_GPU> `gpu::``getColumnSumFilter_GPU`(int sumType, int dstType, int ksize, int anchor=-1)

  Parameters:

  - sumType – Input image type. Only `CV_8UC1` type is supported for now.
  - dstType – Output image type. Only `CV_32FC1` type is supported for now.
  - ksize – Kernel size.
  - anchor – Anchor point. The default value (-1) means that the anchor is at the kernel center.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

## gpu::createBoxFilter_GPU

Creates a normalized 2D box filter.

C++:`` Ptr<FilterEngine_GPU> `gpu::``createBoxFilter_GPU`(int srcType, int dstType, const Size& ksize, const Point& anchor=Point(-1,-1))

C++:`` Ptr<BaseFilter_GPU> `gpu::``getBoxFilter_GPU`(int srcType, int dstType, const Size& ksize, Point anchor=Point(-1, -1))

  Parameters:

  - srcType – Input image type supporting `CV_8UC1` and `CV_8UC4` .
  - dstType – Output image type. It supports only the same values as the source type.
  - ksize – Kernel size.
  - anchor – Anchor point. The default value `Point(-1, -1)` means that the anchor is at the kernel center.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

See also

`boxFilter()`

## gpu::boxFilter

Smooths the image using the normalized box filter.

C++:`` void `gpu::``boxFilter`(const GpuMat& src, GpuMat& dst, int ddepth, Size ksize, Point anchor=Point(-1,-1), Stream& stream=Stream::Null())

  Parameters:

  - src – Input image. `CV_8UC1` and `CV_8UC4` source types are supported.
  - dst – Output image type. The size and type is the same as `src` .
  - ddepth – Output image depth. If -1, the output image has the same depth as the input one. The only values allowed here are `CV_8U` and -1.
  - ksize – Kernel size.
  - anchor – Anchor point. The default value `Point(-1, -1)` means that the anchor is at the kernel center.
  - stream – Stream for the asynchronous version.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

See also

`boxFilter()`

## gpu::blur

Acts as a synonym for the normalized box filter.

C++:`` void `gpu::``blur`(const GpuMat& src, GpuMat& dst, Size ksize, Point anchor=Point(-1,-1), Stream& stream=Stream::Null())

  Parameters:

  - src – Input image. `CV_8UC1` and `CV_8UC4` source types are supported.
  - dst – Output image type with the same size and type as `src` .
  - ksize – Kernel size.
  - anchor – Anchor point. The default value Point(-1, -1) means that the anchor is at the kernel center.
  - stream – Stream for the asynchronous version.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

See also

`blur()`, `gpu::boxFilter()`

## gpu::createMorphologyFilter_GPU

Creates a 2D morphological filter.

C++:`` Ptr<FilterEngine_GPU> `gpu::``createMorphologyFilter_GPU`(int op, int type, const Mat& kernel, const Point& anchor=Point(-1,-1), int iterations=1)

C++:`` Ptr<BaseFilter_GPU> `gpu::``getMorphologyFilter_GPU`(int op, int type, const Mat& kernel, const Size& ksize, Point anchor=Point(-1,-1))

  Parameters:

  - op – Morphology operation id. Only `MORPH_ERODE` and `MORPH_DILATE` are supported.
  - type – Input/output image type. Only `CV_8UC1` and `CV_8UC4` are supported.
  - kernel – 2D 8-bit structuring element for the morphological operation.
  - ksize – Size of a horizontal or vertical structuring element used for separable morphological operations.
  - anchor – Anchor position within the structuring element. Negative values mean that the anchor is at the center.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

See also

`createMorphologyFilter()`

## gpu::erode

Erodes an image by using a specific structuring element.

C++:`` void `gpu::``erode`(const GpuMat& src, GpuMat& dst, const Mat& kernel, Point anchor=Point(-1, -1), int iterations=1 )

C++:`` void `gpu::``erode`(const GpuMat& src, GpuMat& dst, const Mat& kernel, GpuMat& buf, Point anchor=Point(-1, -1), int iterations=1, Stream& stream=Stream::Null() )

  Parameters:

  - src – Source image. Only `CV_8UC1` and `CV_8UC4` types are supported.
  - dst – Destination image with the same size and type as `src` .
  - kernel – Structuring element used for erosion. If `kernel=Mat()`, a 3x3 rectangular structuring element is used.
  - anchor – Position of an anchor within the element. The default value `(-1, -1)` means that the anchor is at the element center.
  - iterations – Number of times erosion to be applied.
  - stream – Stream for the asynchronous version.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

See also

`erode()`

## gpu::dilate

Dilates an image by using a specific structuring element.

C++:`` void `gpu::``dilate`(const GpuMat& src, GpuMat& dst, const Mat& kernel, Point anchor=Point(-1, -1), int iterations=1 )

C++:`` void `gpu::``dilate`(const GpuMat& src, GpuMat& dst, const Mat& kernel, GpuMat& buf, Point anchor=Point(-1, -1), int iterations=1, Stream& stream=Stream::Null() )

  Parameters:

  - src – Source image. `CV_8UC1` and `CV_8UC4` source types are supported.
  - dst – Destination image with the same size and type as `src`.
  - kernel – Structuring element used for dilation. If `kernel=Mat()`, a 3x3 rectangular structuring element is used.
  - anchor – Position of an anchor within the element. The default value `(-1, -1)` means that the anchor is at the element center.
  - iterations – Number of times dilation to be applied.
  - stream – Stream for the asynchronous version.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

See also

`dilate()`

## gpu::morphologyEx

Applies an advanced morphological operation to an image.

C++:`` void `gpu::``morphologyEx`(const GpuMat& src, GpuMat& dst, int op, const Mat& kernel, Point anchor=Point(-1, -1), int iterations=1 )

C++:`` void `gpu::``morphologyEx`(const GpuMat& src, GpuMat& dst, int op, const Mat& kernel, GpuMat& buf1, GpuMat& buf2, Point anchor=Point(-1, -1), int iterations=1, Stream& stream=Stream::Null() )

  Parameters:

  - src – Source image. `CV_8UC1` and `CV_8UC4` source types are supported.
  - dst – Destination image with the same size and type as `src` .
  - op –

    Type of morphological operation. The following types are possible:

    - MORPH_OPEN opening
    - MORPH_CLOSE closing
    - MORPH_GRADIENT morphological gradient
    - MORPH_TOPHAT “top hat”
    - MORPH_BLACKHAT “black hat”
  - kernel – Structuring element.
  - anchor – Position of an anchor within the element. The default value `Point(-1, -1)` means that the anchor is at the element center.
  - iterations – Number of times erosion and dilation to be applied.
  - stream – Stream for the asynchronous version.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

See also

`morphologyEx()`

## gpu::createLinearFilter_GPU

Creates a non-separable linear filter.

C++:`` Ptr<FilterEngine_GPU> `gpu::``createLinearFilter_GPU`(int srcType, int dstType, const Mat& kernel, Point anchor=Point(-1,-1), int borderType=BORDER_DEFAULT)

  Parameters:

  - srcType – Input image type. Supports `CV_8U` , `CV_16U` and `CV_32F` one and four channel image.
  - dstType – Output image type. The same type as `src` is supported.
  - kernel – 2D array of filter coefficients. Floating-point coefficients will be converted to fixed-point representation before the actual processing. Supports size up to 16. For larger kernels use `gpu::convolve()`.
  - anchor – Anchor point. The default value Point(-1, -1) means that the anchor is at the kernel center.
  - borderType – Pixel extrapolation method. For details, see `borderInterpolate()` .

See also

`createLinearFilter()`

## gpu::filter2D

Applies the non-separable 2D linear filter to an image.

C++:`` void `gpu::``filter2D`(const GpuMat& src, GpuMat& dst, int ddepth, const Mat& kernel, Point anchor=Point(-1,-1), int borderType=BORDER_DEFAULT, Stream& stream=Stream::Null())

  Parameters:

  - src – Source image. Supports `CV_8U` , `CV_16U` and `CV_32F` one and four channel image.
  - dst – Destination image. The size and the number of channels is the same as `src` .
  - ddepth – Desired depth of the destination image. If it is negative, it is the same as `src.depth()` . It supports only the same depth as the source image depth.
  - kernel – 2D array of filter coefficients.
  - anchor – Anchor of the kernel that indicates the relative position of a filtered point within the kernel. The anchor resides within the kernel. The special default value (-1,-1) means that the anchor is at the kernel center.
  - borderType – Pixel extrapolation method. For details, see `borderInterpolate()` .
  - stream – Stream for the asynchronous version.

See also

`filter2D()`, `gpu::convolve()`

## gpu::Laplacian

Applies the Laplacian operator to an image.

C++:`` void `gpu::``Laplacian`(const GpuMat& src, GpuMat& dst, int ddepth, int ksize=1, double scale=1, int borderType=BORDER_DEFAULT, Stream& stream=Stream::Null())

  Parameters:

  - src – Source image. `CV_8UC1` and `CV_8UC4` source types are supported.
  - dst – Destination image. The size and number of channels is the same as `src` .
  - ddepth – Desired depth of the destination image. It supports only the same depth as the source image depth.
  - ksize – Aperture size used to compute the second-derivative filters (see `getDerivKernels()`). It must be positive and odd. Only `ksize` = 1 and `ksize` = 3 are supported.
  - scale – Optional scale factor for the computed Laplacian values. By default, no scaling is applied (see `getDerivKernels()` ).
  - borderType – Pixel extrapolation method. For details, see `borderInterpolate()` .
  - stream – Stream for the asynchronous version.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

See also

`Laplacian()`, `gpu::filter2D()`

## gpu::getLinearRowFilter_GPU

Creates a primitive row filter with the specified kernel.

C++:`` Ptr<BaseRowFilter_GPU> `gpu::``getLinearRowFilter_GPU`(int srcType, int bufType, const Mat& rowKernel, int anchor=-1, int borderType=BORDER_DEFAULT )

  Parameters:

  - srcType – Source array type. Only `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` source types are supported.
  - bufType – Intermediate buffer type with as many channels as `srcType` .
  - rowKernel – Filter coefficients. Support kernels with `size <= 16` .
  - anchor – Anchor position within the kernel. Negative values mean that the anchor is positioned at the aperture center.
  - borderType – Pixel extrapolation method. For details, see `borderInterpolate()`. For details on limitations, see below.

There are two versions of the algorithm: NPP and OpenCV.

> - NPP version is called when `srcType == CV_8UC1` or `srcType == CV_8UC4` and `bufType == srcType` . Otherwise, the OpenCV version is called. NPP supports only `BORDER_CONSTANT` border type and does not check indices outside the image.
> - OpenCV version supports only `CV_32F` buffer depth and `BORDER_REFLECT101` , `BORDER_REPLICATE` , and `BORDER_CONSTANT` border types. It checks indices outside the image.

See also

`createSeparableLinearFilter()` .

## gpu::getLinearColumnFilter_GPU

Creates a primitive column filter with the specified kernel.

C++:`` Ptr<BaseColumnFilter_GPU> `gpu::``getLinearColumnFilter_GPU`(int bufType, int dstType, const Mat& columnKernel, int anchor=-1, int borderType=BORDER_DEFAULT )

  Parameters:

  - bufType – Intermediate buffer type with as many channels as `dstType` .
  - dstType – Destination array type. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` destination types are supported.
  - columnKernel – Filter coefficients. Support kernels with `size <= 16` .
  - anchor – Anchor position within the kernel. Negative values mean that the anchor is positioned at the aperture center.
  - borderType – Pixel extrapolation method. For details, see `borderInterpolate()` . For details on limitations, see below.

There are two versions of the algorithm: NPP and OpenCV.

> - NPP version is called when `dstType == CV_8UC1` or `dstType == CV_8UC4` and `bufType == dstType` . Otherwise, the OpenCV version is called. NPP supports only `BORDER_CONSTANT` border type and does not check indices outside the image.
> - OpenCV version supports only `CV_32F` buffer depth and `BORDER_REFLECT101` , `BORDER_REPLICATE` , and `BORDER_CONSTANT` border types. It checks indices outside image.

See also

`gpu::getLinearRowFilter_GPU()`, `createSeparableLinearFilter()`

## gpu::createSeparableLinearFilter_GPU

Creates a separable linear filter engine.

C++:`` Ptr<FilterEngine_GPU> `gpu::``createSeparableLinearFilter_GPU`(int srcType, int dstType, const Mat& rowKernel, const Mat& columnKernel, const Point& anchor=Point(-1,-1), int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1)

  Parameters:

  - srcType – Source array type. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` source types are supported.
  - dstType – Destination array type. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` destination types are supported.
  - rowKernel – Horizontal filter coefficients. Support kernels with `size <= 16` .
  - columnKernel – Vertical filter coefficients. Support kernels with `size <= 16` .
  - anchor – Anchor position within the kernel. Negative values mean that anchor is positioned at the aperture center.
  - rowBorderType – Pixel extrapolation method in the vertical direction For details, see `borderInterpolate()`. For details on limitations, see `gpu::getLinearRowFilter_GPU()`, cpp:ocv:func:gpu::getLinearColumnFilter_GPU.
  - columnBorderType – Pixel extrapolation method in the horizontal direction.

See also

`gpu::getLinearRowFilter_GPU()`, `gpu::getLinearColumnFilter_GPU()`, `createSeparableLinearFilter()`

## gpu::sepFilter2D

Applies a separable 2D linear filter to an image.

C++:`` void `gpu::``sepFilter2D`(const GpuMat& src, GpuMat& dst, int ddepth, const Mat& kernelX, const Mat& kernelY, Point anchor=Point(-1,-1), int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1 )

C++:`` void `gpu::``sepFilter2D`(const GpuMat& src, GpuMat& dst, int ddepth, const Mat& kernelX, const Mat& kernelY, GpuMat& buf, Point anchor=Point(-1,-1), int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1, Stream& stream=Stream::Null() )

  Parameters:

  - src – Source image. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_32SC1` , `CV_32FC1` source types are supported.
  - dst – Destination image with the same size and number of channels as `src` .
  - ddepth – Destination image depth. `CV_8U` , `CV_16S` , `CV_32S` , and `CV_32F` are supported.
  - kernelX – Horizontal filter coefficients.
  - kernelY – Vertical filter coefficients.
  - anchor – Anchor position within the kernel. The default value `(-1, 1)` means that the anchor is at the kernel center.
  - rowBorderType – Pixel extrapolation method in the vertical direction. For details, see `borderInterpolate()`.
  - columnBorderType – Pixel extrapolation method in the horizontal direction.
  - stream – Stream for the asynchronous version.

See also

`gpu::createSeparableLinearFilter_GPU()`, `sepFilter2D()`

## gpu::createDerivFilter_GPU

Creates a filter engine for the generalized Sobel operator.

C++:`` Ptr<FilterEngine_GPU> `gpu::``createDerivFilter_GPU`(int srcType, int dstType, int dx, int dy, int ksize, int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1)

  Parameters:

  - srcType – Source image type. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` source types are supported.
  - dstType – Destination image type with as many channels as `srcType` , `CV_8U` , `CV_16S` , `CV_32S` , and `CV_32F` depths are supported.
  - dx – Derivative order in respect of x.
  - dy – Derivative order in respect of y.
  - ksize – Aperture size. See `getDerivKernels()` for details.
  - rowBorderType – Pixel extrapolation method in the vertical direction. For details, see `borderInterpolate()`.
  - columnBorderType – Pixel extrapolation method in the horizontal direction.

See also

`gpu::createSeparableLinearFilter_GPU()`, `createDerivFilter()`

## gpu::Sobel

Applies the generalized Sobel operator to an image.

C++:`` void `gpu::``Sobel`(const GpuMat& src, GpuMat& dst, int ddepth, int dx, int dy, int ksize=3, double scale=1, int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1 )

C++:`` void `gpu::``Sobel`(const GpuMat& src, GpuMat& dst, int ddepth, int dx, int dy, GpuMat& buf, int ksize=3, double scale=1, int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1, Stream& stream=Stream::Null() )

  Parameters:

  - src – Source image. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` source types are supported.
  - dst – Destination image with the same size and number of channels as source image.
  - ddepth – Destination image depth. `CV_8U` , `CV_16S` , `CV_32S` , and `CV_32F` are supported.
  - dx – Derivative order in respect of x.
  - dy – Derivative order in respect of y.
  - ksize – Size of the extended Sobel kernel. Possible values are 1, 3, 5 or 7.
  - scale – Optional scale factor for the computed derivative values. By default, no scaling is applied. For details, see `getDerivKernels()` .
  - rowBorderType – Pixel extrapolation method in the vertical direction. For details, see `borderInterpolate()`.
  - columnBorderType – Pixel extrapolation method in the horizontal direction.
  - stream – Stream for the asynchronous version.

See also

`gpu::createSeparableLinearFilter_GPU()`, `Sobel()`

## gpu::Scharr

Calculates the first x- or y- image derivative using the Scharr operator.

C++:`` void `gpu::``Scharr`(const GpuMat& src, GpuMat& dst, int ddepth, int dx, int dy, double scale=1, int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1 )

C++:`` void `gpu::``Scharr`(const GpuMat& src, GpuMat& dst, int ddepth, int dx, int dy, GpuMat& buf, double scale=1, int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1, Stream& stream=Stream::Null() )

  Parameters:

  - src – Source image. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` source types are supported.
  - dst – Destination image with the same size and number of channels as `src` has.
  - ddepth – Destination image depth. `CV_8U` , `CV_16S` , `CV_32S` , and `CV_32F` are supported.
  - dx – Order of the derivative x.
  - dy – Order of the derivative y.
  - scale – Optional scale factor for the computed derivative values. By default, no scaling is applied. See `getDerivKernels()` for details.
  - rowBorderType – Pixel extrapolation method in the vertical direction. For details, see `borderInterpolate()`.
  - columnBorderType – Pixel extrapolation method in the horizontal direction.
  - stream – Stream for the asynchronous version.

See also

`gpu::createSeparableLinearFilter_GPU()`, `Scharr()`

## gpu::createGaussianFilter_GPU

Creates a Gaussian filter engine.

C++:`` Ptr<FilterEngine_GPU> `gpu::``createGaussianFilter_GPU`(int type, Size ksize, double sigma1, double sigma2=0, int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1 )

  Parameters:

  - type – Source and destination image type. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` are supported.
  - ksize – Aperture size. See `getGaussianKernel()` for details.
  - sigma1 – Gaussian sigma in the horizontal direction. See `getGaussianKernel()` for details.
  - sigma2 – Gaussian sigma in the vertical direction. If 0, then \texttt{sigma2}\leftarrow\texttt{sigma1} .
  - rowBorderType – Pixel extrapolation method in the vertical direction. For details, see `borderInterpolate()`.
  - columnBorderType – Pixel extrapolation method in the horizontal direction.

See also

`gpu::createSeparableLinearFilter_GPU()`, `createGaussianFilter()`

## gpu::GaussianBlur

Smooths an image using the Gaussian filter.

C++:`` void `gpu::``GaussianBlur`(const GpuMat& src, GpuMat& dst, Size ksize, double sigma1, double sigma2=0, int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1 )

C++:`` void `gpu::``GaussianBlur`(const GpuMat& src, GpuMat& dst, Size ksize, GpuMat& buf, double sigma1, double sigma2=0, int rowBorderType=BORDER_DEFAULT, int columnBorderType=-1, Stream& stream=Stream::Null() )

  Parameters:

  - src – Source image. `CV_8UC1` , `CV_8UC4` , `CV_16SC1` , `CV_16SC2` , `CV_16SC3` , `CV_32SC1` , `CV_32FC1` source types are supported.
  - dst – Destination image with the same size and type as `src` .
  - ksize – Gaussian kernel size. `ksize.width` and `ksize.height` can differ but they both must be positive and odd. If they are zeros, they are computed from `sigma1` and `sigma2` .
  - sigma1 – Gaussian kernel standard deviation in X direction.
  - sigma2 – Gaussian kernel standard deviation in Y direction. If `sigma2` is zero, it is set to be equal to `sigma1` . If they are both zeros, they are computed from `ksize.width` and `ksize.height`, respectively. See `getGaussianKernel()` for details. To fully control the result regardless of possible future modification of all this semantics, you are recommended to specify all of `ksize` , `sigma1` , and `sigma2` .
  - rowBorderType – Pixel extrapolation method in the vertical direction. For details, see `borderInterpolate()`.
  - columnBorderType – Pixel extrapolation method in the horizontal direction.
  - stream – Stream for the asynchronous version.

See also

`gpu::createGaussianFilter_GPU()`, `GaussianBlur()`

## gpu::getMaxFilter_GPU

Creates the maximum filter.

C++:`` Ptr<BaseFilter_GPU> `gpu::``getMaxFilter_GPU`(int srcType, int dstType, const Size& ksize, Point anchor=Point(-1,-1))

  Parameters:

  - srcType – Input image type. Only `CV_8UC1` and `CV_8UC4` are supported.
  - dstType – Output image type. It supports only the same type as the source type.
  - ksize – Kernel size.
  - anchor – Anchor point. The default value (-1) means that the anchor is at the kernel center.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

## gpu::getMinFilter_GPU

Creates the minimum filter.

C++:`` Ptr<BaseFilter_GPU> `gpu::``getMinFilter_GPU`(int srcType, int dstType, const Size& ksize, Point anchor=Point(-1,-1))

  Parameters:

  - srcType – Input image type. Only `CV_8UC1` and `CV_8UC4` are supported.
  - dstType – Output image type. It supports only the same type as the source type.
  - ksize – Kernel size.
  - anchor – Anchor point. The default value (-1) means that the anchor is at the kernel center.

Note

This filter does not check out-of-border accesses, so only a proper sub-matrix of a bigger matrix has to be passed to it.

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