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IMAQ Optical Flow (HS) VI

NI Vision 2011 for LabVIEW Help

Edition Date: June 2011

Part Number: 370281P-01

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Owning Palette: Motion Estimation
Requires: NI Vision Development Module

Computes the optical flow (velocity flow) information in two successive images using the Horn and Schunck algorithm.

IMAQ Optical Flow (HS)

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Stopping Criteria specifies the conditions that need to be met to stop the optical flow computation.

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Type specifies the type of stopping criteria to use: Iteration, Epsilon, or Both.

Choose one of the following criteria.

Iterations (1)

Specifies that the computation should stop after the number of iterations in the Max. Iterations control.

Epsilon (2)

Specifies the computation should stop after the value of Epsilon has been reached.

Both (3)

Specifies the computation should stop after the maximum iterations and Epsilon value have both been reached.

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Max. Iterations specifies the maximum iterations to run the optical flow computation.

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Epsilon specifies the maximum difference allowed between the velocity information computed between two successive iterations.

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ROI Descriptor is a descriptor that defines the Region of Interest (ROI) within which the optical flow is computed.

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Global Rectangle contains the coordinates of the bounding rectangle.

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Contours are each of the individual shapes that define an ROI.

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ID refers to whether the contour is the external or internal edge of an ROI.

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Type is the shape type of the contour.

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Coordinates indicates the relative position of the contour.

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Current Frame is a reference to the current source image.

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Previous Frame is a reference to the previous source image.

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Smoothing Parameter specifies the smoothing effect to apply to the velocity information in the image.

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Velocity Component 1 In is a reference to the image that will contain the horizontal component or the magnitude component of the computed velocity at each pixel.

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Velocity Component 2 In is a reference to the image that will contain the vertical component or the phase component of the computed velocity at each pixel.

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error in (no error) describes the error status before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.

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status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE.

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code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.

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source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.

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Velocity Representation specifies whether the computed velocity information should be represented in Cartesian or polar coordinates.

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Use Previous, when TRUE, uses the information in Velocity Component 1 In and Velocity Component 2 In as the initial estimates of the velocity to compute the current velocity.

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Current Frame Out (dup) is a duplicate of the input Current Frame.

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Velocity Component 1 Out is a reference to the image that contains the horizontal component or the magnitude component of the computed velocity at each pixel.

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Velocity Component 2 Out is a reference to the image that contains the vertical component or the phase component of the computed velocity at each pixel.

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error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out indicator on the front panel and select Explain Error from the shortcut menu for more information about the error.

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status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.

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code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.

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source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.


 

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