NI Vision for LabVIEW

IMAQ Feature Point Descriptor VI

  • Updated2023-02-21
  • 4 minute(s) read
Owning Palette: Feature Correspondence
Requires: NI Vision Development Module

Computes feature descriptor vectors for each feature point. Supported feature descriptors are fast retina keypoint (FREAK) and binary robust invariant scalable keypoints (BRISK).

Examples

IMAQ Feature Point Descriptor

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Image is a reference to the source image.

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Feature Point Coordinates In inputs the locations of the feature points detected in the image

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X is the x-coordinate of the point.

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Y is the y-coordinate of the point.

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Feature descriptor method chooses the descriptor method. The following options area available.

FREAK (0)

is a binary descriptor that provides information about feature points. FREAK provides better matches than BRISK when there is rotation invariance. Both algorithms provide similar results when there are changes in scale.

BRISK (1)

is a binary descriptor that provides information about feature points. BRISK provides better matches than FREAK when there are changes in perspective distortion. Both algorithms provide similar results when there are changes in scale.

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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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Image (duplicate) is the reference to the image that contains corners.

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Feature Point Coordinates Out returns the locations of the feature points detected in the image

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X is the x-coordinate of the point.

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Y is the y-coordinate of the point.

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Feature Descriptors returns the descriptors for all the detected feature points.

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Descriptor

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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.

Examples

Refer to the following for an example that uses this VI.

  • LabVIEW\examples\Vision\Feature Correspondence\Feature Matching.vi