IMAQ Find Edge VI

LabView NI Vision

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IMAQ Find Edge VI

Owning Palette: Locate EdgesInstalled With: NI Vision Development Module

Finds straight edges (lines) within a region in an image.

IMAQ Find Edge

Options is a cluster defining the parameters of the edge detection algorithm and the information that is overlaid on the result image.

Search Direction specifies the direction in which the Region of Interest (ROI) is examined when straight edge detection is performed.

Left to Right (0)	(Default) Searches for edges from left to right
Right to Left (1)	Searches for edges from right to left
Top to Bottom (2)	Searches for edges from top to bottom
Bottom to Top (3)	Searches for edges from bottom to top

Edge Options specifies the parameters that are used to compute the edge gradient information and detect the edges.

Edge Polarity specifies the polarity of the edges to be found.

All Edges (0)	(Default) Searches for all edges
Rising Edges (1)	Searches for rising edges
Falling Edges (2)	Searches for falling edges

Kernel Size specifies the size of the edge detection kernel. The default is 3.

Width specifies the number of pixels averaged perpendicular to the search direction to compute the edge profile strength at each point along the search ROI. The default is 3.

Minimum Edge Strength specifies the minimum edge strength (gradient magnitude) required for a detected edge. The default is 10.

Interpolation Type specifies the interpolation method used to locate the edge position. Choose from the following options:

Zero Order (0)	Rounds to the nearest integral edge location
Bilinear (1)	Uses bilinear interpolation to compute the edge location
Bilinear Fixed (4)	(Default) Uses the fixed-point computation of bilinear interpolation to determine the edge location

Data Processing Method is the method used to process the data extracted for edge detection.

Average (0)	(Default) Averages the data extracted for edge detection
Median (1)	Takes the median of the data extracted for edge detection

Show Search Area determines whether the search area is overlaid on the image.

Show Search Lines determines whether the search lines used to locate the edges are overlaid on the image.

Show Edges Found determines whether the locations of the edges found are overlaid on the result image.

Show Result determines whether the coordinate system found is overlaid on the result image.

Search Area Color specifies the color to use to overlay the search area.

Search Lines Color specifies the color to use to overlay the search lines.

Edge Locations Color specifies the color to use to overlay the edge locations.

Result Color specifies the color to use to overlay the result.

Overlay Group Name specifies the overlay group name for the step overlays.

Image is a reference to the image in which you want to search.

ROI Descriptor is a descriptor that defines the rectangle, rotated rectangle, or other four-side rectangular polygon within which the edge detection is performed.

Global Rectangle contains the coordinates of the bounding rectangle.

Contours are each of the individual shapes that define an ROI.

	ID refers to whether the contour is the external or internal edge of an ROI.
	Type is the shape type of the contour.
	Coordinates indicates the relative position of the contour.

Coordinate System specifies the coordinate system to use.

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.

	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.
	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.
	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.

Line Fit Options specifies the options that are used to detect the straight edges.

Number of Lines specifies the number of straight edges to find. The default is 1.

Type specifies the method used to find the straight edge. Choose from the following options:

First Edge Rake (0)	(Default) Fits a straight edge on the first points detected using a Rake
Best Edge Rake (1)	Fits a straight edge on the best points detected using a Rake
Hough Edge Rake (2)	Finds the strongest straight edge using all points detected on a Rake
First Edge Projection (3)	Uses the location of the first projected edge as the straight edge
Best Edge Projection (4)	Finds the strongest projected edge location to determine the straight edge

Min. Score specifies the minimum score of a detected straight edge. The default is 10.

Max. Score specifies the maximum score of a detected straight edge. The default is 1000.

Orientation specifies the angle at which the straight edge is expected to be found. The default is 0.

Angle Range specifies the positive and negative range around the Orientation within which the straight edge is expected to be found. The default is 45.

Angle Tolerance specifies the expected angular accuracy of the straight edge. The default is 1.

Step Size specifies the gap in pixels between the search lines used with the Rake-based methods. The default is 7.

Min. SNR (db) specifies the minimum signal to noise ratio (SNR) of the edge points used to fit the straight edge. The default is 0.

Min. Points (%) specifies the minimum number for points as a percentage of the number of search lines that need to be included in the detected straight edge. The default is 25%.

Hough Iterations specify the number of iterations used in the Hough-based method. The default is 5.

Image Out is a reference to Image.

Coordinate System (duplicate) is a reference to the coordinate system.

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.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.
	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.
	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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