Table Of Contents

Max Clamp (G Dataflow)

Last Modified: June 25, 2019

Finds edges along a region of interest (rotated rectangle only) and measures the distance between the furthest opposed points on the edges found.

Edges are determined by extracting contours from the ROI and analyzing their order and geometry. When valid calibration information is present, the distance is measured in pixels and real-world units.

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overlay options

Cluster defining the information to be overlaid on the resulting image.

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show search area

Boolean that specifies if the ROI is overlaid on the image.

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show curves

Boolean that specifies if curves are overlaid on the image.

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show clamp locations

Boolean that specifies if the clamp locations are overlaid on the image.

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show result

Boolean that specifies if the result of the clamp calculation is overlaid on the resulting image.

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search area color

Color used to overlay the search area.

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curves color

Color used to overlay the curves.

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clamp locations color

Color used to overlay the clamp locations.

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result color

Color used to overlay the result.

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overlay group name

Group name for the step overlays.

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image in

Reference to the source image.

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ROI descriptor

Rotated rectangle within which to perform the clamp.

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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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curve extraction options

Cluster containing information about how curves are extracted from the image.

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Extraction Mode

Input that specifies how the node identifies curves in the image.

Name Value Description
Normal 0

(Default) Select if you want the node to make no assumptions about the uniformity of objects in the image or the image background.

Uniform Regions 1

Select if you want the node to assume that either the objects in the image or the image background consist of uniform pixel values. This allows the node to more accurately calculate the external curves of the objects.

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Edge Threshold

Minimum contrast a seed point must have for it to begin a curve.

Valid values range from 1 to 255.

Default: 75

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Edge Filter Size

Width of the edge filter that the node uses to identify curves in the image.

Name Value Description
Fine 0

Sets to fine edge filter size.

Normal 1

(Default) Sets to normal edge filter size.

Contour Tracing 2

Sets to contour tracing edge filter size, which provides the best results for contour extraction but increases the time required to process the image.

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Min Length

Length, in pixels, of the smallest curve that you want the node to identify.

The node ignores any curves that have a length less than this value.

Default: 25

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Row Search Step Size

Distance, in the y direction, between the image rows that the algorithm inspects for curve seed points.

Valid values range from 1 to 255.

Default: 15

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Col Search Step Size

Distance, in the x direction, between the image columns that the algorithm inspects for curve seed points.

Valid values range from 1 to 255.

Default: 15

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Max Endpoint Gap

Maximum gap, in pixels, between the endpoints of a curve that the node identifies as a closed curve.

If the gap is larger than this value, the node identifies the curve as an open curve.

Default: 10

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Closed

Boolean value that specifies only closed curves are identified in the image.

TRUE Identifies only closed curves.
FALSE Identifies both open and closed curves.

Default: FALSE

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Subpixel

Boolean value that specifies if curve points are detected with subpixel accuracy.

TRUE Curve points are detected with subpixel accuracy.
FALSE Curve points are not detected with subpixel accuracy.

Default: FALSE

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coordinate system

Coordinate system to which the ROI descriptor is linked.

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reference system

Cluster containing origin, angle (deg), and axis reference.

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origin

Point cluster that specifies the origin of the base-reference coordinate system.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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angle (deg)

Angle that the base-reference coordinate system makes with the image coordinate system.

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axis reference

Element defined as direct or indirect.

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measurement system

Cluster containing origin, angle (deg), and axis reference.

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origin

Point cluster that specifies the origin of the base-reference coordinate system.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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angle (deg)

Angle that the base-reference coordinate system makes with the image coordinate system.

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axis reference

Element defined as direct or indirect.

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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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clamp options

Cluster that controls the behavior of the clamp.

You can control the angle tolerance of the clamp and the edge polarity of the curves.

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angle range (+/-)

Tolerance, in degrees, of the rotated rectangle ROI.

This value can range from 0 to 180.

Default: 5 degrees

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edge polarity

Polarity of the edges.

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start

Starting polarity of the edge.

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end

End polarity of the edge.

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image out

Reference to image in.

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clamp results

Cluster that shows the measured distances and angles for the applied clamp.

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distance (pixels)

Distance, in pixels, measured by the clamp.

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distance (real world)

Distance, in real world units, measured by the clamp.

The node provides this measurement when the input image is calibrated.

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angle (absolute)

Absolute angle of the clamp.

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angle (relative)

Angle of the clamp, with respect to the ROI angle.

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clamp points

Cluster specifying the locations of the clamp start and end points, both in pixel and real-world coordinates.

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pixels

Start and end points of the clamp in pixels.

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start

Start point of the clamp.

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x

X-coordinate of the point.

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y

Y-coordinate of the point.

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end

End point of the clamp.

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x

X-coordinate of the point.

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y

Y-coordinate of the point.

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real world

Start and end points of the clamp in real world units.

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start

Start point of the clamp.

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x

X-coordinate of the point.

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y

Y-coordinate of the point.

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end

End point of the clamp.

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x

X-coordinate of the point.

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y

Y-coordinate of the point.

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coordinate system dup

Reference to the coordinate system.

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reference system

Cluster containing origin, angle (deg), and axis reference.

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origin

Point cluster that specifies the origin of the base-reference coordinate system.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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angle (deg)

Angle that the base-reference coordinate system makes with the image coordinate system.

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axis reference

Reference to the axis defined as direct or indirect.

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measurement system

Cluster containing origin, angle (deg), and axis reference.

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origin

Point cluster that specifies the origin of the base-reference coordinate system.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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angle (deg)

Angle that the base-reference coordinate system makes with the image coordinate system.

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axis reference

Reference to the axis defined as direct or indirect.

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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?

Boolean that specifies if the calibration information in the image is valid.

TRUE Calibration information is available to compute the clamp in real-world units.
FALSE Calibration information is not available.

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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