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Computes dense optical flow using Gunnar Farneback's algorithm

**Namespace:** Emgu.CV**Assembly:** Emgu.CV (in Emgu.CV.dll) Version: 2.4.2.1777 (2.4.2.1777)

# Syntax

C# |
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public static void Farneback( Image<Gray, byte> prev0, Image<Gray, byte> next0, Image<Gray, float> flowX, Image<Gray, float> flowY, double pyrScale, int levels, int winSize, int iterations, int polyN, double polySigma, OPTICALFLOW_FARNEBACK_FLAG flags ) |

Visual Basic |
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Public Shared Sub Farneback ( _ prev0 As Image(Of Gray, Byte), _ next0 As Image(Of Gray, Byte), _ flowX As Image(Of Gray, Single), _ flowY As Image(Of Gray, Single), _ pyrScale As Double, _ levels As Integer, _ winSize As Integer, _ iterations As Integer, _ polyN As Integer, _ polySigma As Double, _ flags As OPTICALFLOW_FARNEBACK_FLAG _ ) |

Visual C++ |
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public: static void Farneback( Image<Gray, unsigned char>^ prev0, Image<Gray, unsigned char>^ next0, Image<Gray, float>^ flowX, Image<Gray, float>^ flowY, double pyrScale, int levels, int winSize, int iterations, int polyN, double polySigma, OPTICALFLOW_FARNEBACK_FLAG flags ) |

#### Parameters

- prev0
- Type: Emgu.CV..::..Image<(Of <(<'Gray, Byte>)>)>

The first 8-bit single-channel input image

- next0
- Type: Emgu.CV..::..Image<(Of <(<'Gray, Byte>)>)>

The second input image of the same size and the same type as prevImg

- flowX
- Type: Emgu.CV..::..Image<(Of <(<'Gray, Single>)>)>

The computed flow image for x-velocity; will have the same size as prevImg

- flowY
- Type: Emgu.CV..::..Image<(Of <(<'Gray, Single>)>)>

The computed flow image for y-velocity; will have the same size as prevImg

- pyrScale
- Type: System..::..Double

Specifies the image scale (!1) to build the pyramids for each image. pyrScale=0.5 means the classical pyramid, where each next layer is twice smaller than the previous

- levels
- Type: System..::..Int32

The number of pyramid layers, including the initial image. levels=1 means that no extra layers are created and only the original images are used

- winSize
- Type: System..::..Int32

The averaging window size; The larger values increase the algorithm robustness to image noise and give more chances for fast motion detection, but yield more blurred motion field

- iterations
- Type: System..::..Int32

The number of iterations the algorithm does at each pyramid level

- polyN
- Type: System..::..Int32

Size of the pixel neighborhood used to find polynomial expansion in each pixel. The larger values mean that the image will be approximated with smoother surfaces, yielding more robust algorithm and more blurred motion field. Typically, poly n=5 or 7

- polySigma
- Type: System..::..Double

Standard deviation of the Gaussian that is used to smooth derivatives that are used as a basis for the polynomial expansion. For poly n=5 you can set poly sigma=1.1, for poly n=7 a good value would be poly sigma=1.5

- flags
- Type: Emgu.CV.CvEnum..::..OPTICALFLOW_FARNEBACK_FLAG

The operation flags