Table Of Contents

Rotation Detect (G Dataflow)

Last Modified: June 25, 2019

Detects the rotational shift between two images.

Detection generally occurs between a reference image, with the part being inspected at a known orientation, and another image that has the part in an unknown position. This node extracts pixel values around a circular region in the reference image. These values then are compared to the same region inimage 2. The algorithm looks for the rotational shift between those two samples. To speed up the process, adjust the requested precision of the result.

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reference image

Reference to the image containing the part to be inspected at a known position.

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image 2

Reference to the image that contains the part to be inspected at an unknown rotational shift.

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reference center

Coordinates of the center of a circular region in the reference image.

Pixel values along this region in the reference image are used as features for computing the rotational shift.

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image 2 center

Coordinates of the center of a circular region in image 2.

The pixel values along this region in image 2 are used to compute the rotational shift.

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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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radius

Radius of the circular regions in both images.

Pixel values along this region in the two images are used to detect the rotation angle between the two images.

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precision (degrees)

Sampling period of the pixel values extracted from the circular region.

The speed of this node is affected directly by the sampling period. If the sampling period is high, or the number of samples along the circular region are few, the processing speed of the node increases at the cost of reduced accuracy in the computed rotational shift. In many cases, a precision higher than five degrees is not needed to position the regions of inspection of a part.

Default: 5

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angle (radians)

Angle in radians corresponding to the shift giving the best match between the two samples.

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angle (degrees)

Angle in degrees corresponding to the shift giving the best match between the two samples.

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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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