Table Of Contents

Concentric Rake (G Dataflow)

Last Modified: June 25, 2019

Finds edges along concentric circular or angular paths in the image.

Edges are determined based on their contrast and slope.

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optimized mode?

Boolean that enables a faster edge detection algorithm that does not return an edge map.

TRUE Enables a faster edge detection algorithm that does not return an edge map.
FALSE Enables a standard edge detection algorithm that returns an edge map.

Default: TRUE

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edge options

Inputs used to compute the edge gradient information and detect the edges.

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edge polarity

Polarity of the edges to be found.

Name Value Description
all edges 0

(Default) Searches for all edges

rising edges 1

Searches for rising edges

falling edges 2

Searches for falling edges

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kernel size

Size of the edge detection kernel.

Default: 3

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width

Number of pixels averaged perpendicular to the search direction to compute the edge profile strength at each point along the search ROI.

Default: 3

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minimum edge strength

Minimum edge strength, or gradient magnitude, required for a detected edge.

Default: 10

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interpolation type

Interpolation method used to locate the edge position.

Name Description
zero order Rounds to the nearest integral edge location
bilinear Uses bilinear interpolation to compute the edge location
bilinear fixed (Default) Uses the fixed-point computation of bilinear interpolation to determine the edge location
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data processing method

Method used to process the data extracted for edge detection.

Name Description
average (Default) Averages the data extracted for edge detection
median Takes the median of the data extracted for edge detection
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image in

Reference to the source image.

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ROI descriptor

Circular or annular region within which concentric paths are defined.

The ROI must be an annulus.

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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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scan direction

Direction in which the node searches for edges along the concentric search lines.

The following options are valid:

Name Value Description
counterclockwise 0

Searches for edges in a counterclockwise direction.

clockwise 1

Searches for edges in a clockwise direction.

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step size

Radial distance, in pixels, between each concentric line in the annular region.

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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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process

Type of search returned.

Name Description
get first edge Returns the first edge.
get first + last edge Returns the first and last edge.
get all edges Returns all edges found along the search path(s).
get best edge Returns the strongest edges found along the search path(s).

Default: get all edges

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image out

Reference to the source image.

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first edges

Information about all edges detected as first edges.

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location (pixel)

Location of the edge point in the image in pixel units.

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location (real-world)

Location of the edge point in the image in calibrated units.

When the image is not calibrated, this is the location in pixel units.

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distance (pixel)

Location of the edge from the first point of the search line along the boundary of the input ROI in pixels.

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distance (real-world)

Location of the edge from the first point of the search line along the boundary of the input ROI in calibrated units.

When the image is not calibrated, this distance is in pixel units.

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strength

Strength, or gradient magnitude, at the located edge.

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noise

Strength of the noise associated with the current edge.

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rising?

Boolean that specifies the polarity of the edge.

TRUE The edge is a rising edge.
FALSE The edge is not a rising edge.
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last edges

Information about all edges detected as last edges.

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location (pixel)

Location of the edge point in the image in pixel units.

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location (real-world)

Location of the edge point in the image in calibrated units.

When the image is not calibrated, this is the location in pixel units.

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distance (pixel)

Location of the edge from the first point of the search line along the boundary of the input ROI in pixels.

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distance (real-world)

Location of the edge from the first point of the search line along the boundary of the input ROI in calibrated units.

When the image is not calibrated, this distance is in pixel units.

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strength

Strength, or gradient magnitude, at the located edge.

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noise

Strength of the noise associated with the current edge.

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rising?

Boolean that specifies the polarity of the edge.

TRUE The edge is a rising edge.
FALSE The edge is not a rising edge.
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search arcs

Information about the search arcs used to detect edges

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center point

Point-coordinate cluster that describes the (x, y) coordinates of the center of the search arc.

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radius

Radius, in pixels, of the search arc.

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start angle

First angle of the circular strip.

The angle is measured counterclockwise from the x-axis of a coordinate system centered on the center of the circle or annulus.

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end angle

Second angle of the circular strip.

The angle is measured counterclockwise from the x-axis of a coordinate system centered on the center of the circle or annulus.

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edge info

Array that contains information about each detected edge along the search arc.

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location (pixel)

Location of the edge point in the image in pixel units.

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location (real-world)

Location of the edge point in the image in calibrated units.

When the image is not calibrated, this is the location in pixel units.

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distance (pixel)

Location of the edge from the first point of the search line along the boundary of the input ROI in pixels.

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distance (real-world)

Location of the edge from the first point of the search line along the boundary of the input ROI in calibrated units.

When the image is not calibrated, this distance is in pixel units.

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strength

Strength, or gradient magnitude, at the located edge.

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noise

Strength of the noise associated with the current edge.

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rising?

Boolean that specifies the polarity of the edge.

TRUE The edge is a rising edge.
FALSE The edge is not a rising edge.
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edge map

Array that contains the calculated edge strengths along the search line.

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calibration valid

Boolean that indicates if the calibration information associated with the edges found along the search line is valid.

TRUE Calibration information is valid.
FALSE Calibration information is invalid for any pixel that is used for edge detection.
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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.

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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