Table Of Contents

FAST Feature Point Detector (G Dataflow)

Last Modified: October 26, 2017

Detects corners in an image using the features from accelerated segment test (FAST) algorithm.

FAST selects features so that they are consistently detected across various transformations, such as blurring, rotation, and scale.

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image in

Reference to the source image.

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ROI descriptor

Region within which to search for corners.

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global rectangle

Coordinates of the bounding rectangle.

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contours

Individual shapes that define an ROI.

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ID

Object specifying if contour is the external or internal edge of an ROI.

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Type

Shape type of the contour.

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Coordinates

Relative position of the contour.

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min feature point strength

Minimum strength required for a point to qualify as a feature point.

The maximum strength value is determined by the bit depth of the image.

Default: 32

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suppress weak points

Boolean that indicates if insignificant feature points are suppressed.

Because FAST detects many features, redundant features of low strength will be found near features of high strength. Use this parameter to remove the redundant features.

True Insignificant feature points are suppressed.
False Insignificant feature points are not suppressed.

Default: True

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error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

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image out

Reference to the source image.

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feature point coordinates (pixel)

Locations of the feature points detected in the image.

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x

X-coordinate of the point.

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y

Y-coordinate of the point.

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feature point coordinates (real-world)

Read world locations of the feature points detected in the calibrated image.

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x

X-coordinate of the point.

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y

Y-coordinate of the point.

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feature point strengths

Strength of the feature points detected in the image.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.
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calibration valid flags

Boolean that indicates if the calibration information associated with the corners found is valid.

Invalid calibration information occurs when a pixel lies outside the area of the image that was calibrated.

True Calibration information is valid.
False Calibration information is invalid.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application


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