CogLineMax ClassCognex VisionPro 9.8 SR1
This class provides functionality for finding lines in images. It will return candidate lines that meet the requirements specified by its properties.
Inheritance Hierarchy

System Object
  System MarshalByRefObject
    Cognex.VisionPro.Implementation CogObjectBase
      Cognex.VisionPro.Implementation CogSerializableObjectBase
        Cognex.VisionPro.Implementation CogSerializableChangedEventBase
          Cognex.VisionPro.LineMax CogLineMax

Namespace: Cognex.VisionPro.LineMax
Assembly: Cognex.VisionPro.LineMax (in Cognex.VisionPro.LineMax.dll) Version: 75.0.0.0
Syntax

[SerializableAttribute]
public class CogLineMax : CogSerializableChangedEventBase

The CogLineMax type exposes the following members.

Constructors

  NameDescription
Public methodCogLineMax 
Constructs a new instance of this class.
Public methodCogLineMax(CogLineMax)
Constructs a deep copy of the supplied instance.
Protected methodCogLineMax(SerializationInfo, StreamingContext)
Serialization constructor.
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Methods

  NameDescription
Public methodCreateObjRef
Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object.
(Inherited from MarshalByRefObject.)
Public methodEquals
Determines whether the specified Object is equal to the current Object.
(Inherited from Object.)
Public methodExecute(ICogImage, ICogRegion)
Performs line finding on the supplied image. The inspection results are stored in a CogLineMaxResults object.
Public methodExecute(IEnumerable ICogImage , IEnumerable ICogRegion )
Performs line finding on the supplied images. The inspection results are stored in a CogLineMaxResults object.
Public methodExecute(ICogImage, ICogRegion, CogImage8Grey, Int32, Int32)
Performs line finding on the supplied image. The inspection results are stored in a CogLineMaxResults object.
Public methodExecute(IEnumerable ICogImage , IEnumerable ICogRegion , IEnumerable CogImage8Grey , IEnumerable Int32 , IEnumerable Int32 )
Performs line finding on the supplied images. The inspection results are stored in a CogLineMaxResults object.
Protected methodFinalize
Allows an Object to attempt to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection.
(Inherited from Object.)
Protected methodGetAttributes
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetClassName
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetComponentName
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetConverter
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetDefaultEvent
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetDefaultProperty
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetEditor
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetEvents 
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetEvents( Attribute )
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Public methodGetHashCode
Serves as a hash function for a particular type.
(Inherited from Object.)
Public methodGetLifetimeService
Retrieves the current lifetime service object that controls the lifetime policy for this instance.
(Inherited from MarshalByRefObject.)
Protected methodGetObjectData
Implements the GetObjectData method of the ISerializable interface.
(Inherited from CogSerializableObjectBase.)
Protected methodGetProperties 
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetProperties( Attribute )
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Protected methodGetPropertyOwner
Implements the corresponding member of the ICustomTypeDescriptor interface. May be overridden in derived classes to provide custom type information.
(Inherited from CogObjectBase.)
Public methodGetType
Gets the Type of the current instance.
(Inherited from Object.)
Public methodInitializeLifetimeService
Obtains a lifetime service object to control the lifetime policy for this instance.
(Inherited from MarshalByRefObject.)
Protected methodMemberwiseClone 
Creates a shallow copy of the current Object.
(Inherited from Object.)
Protected methodMemberwiseClone(Boolean)
Creates a shallow copy of the current MarshalByRefObject object.
(Inherited from MarshalByRefObject.)
Protected methodOnChanged(Int64)
This method should be called internally whenever the object's state may have changed.
(Inherited from CogSerializableChangedEventBase.)
Protected methodOnChanged(CogChangedEventArgs)
This method may be called internally whenever a derived object's state may have changed and the derived object expresses this change via a derived CogChangedEventArgs class.
(Inherited from CogSerializableChangedEventBase.)
Public methodResumeAndRaiseChangedEvent
Re-enables raising of the Changed event after SuspendChangedEvent has been called, and raises the Changed event if the ChangedEventSuspended count is reduced to zero and any changes were made while events were suspended. Must be called once for each call to SuspendChangedEvent.
(Inherited from CogSerializableChangedEventBase.)
Public methodSuspendChangedEvent
Temporarily suspends the raising of the Changed event. May be called more than once, and a corresponding call to ResumeAndRaiseChangedEvent must be made for each call to SuspendChangedEvent.
(Inherited from CogSerializableChangedEventBase.)
Public methodToString
Returns a String that represents the current Object.
(Inherited from Object.)
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Fields

  NameDescription
Public fieldStatic memberSfAssurance
This bit will be set in the EventArgs of a Changed event every time the value returned by Assurance may have changed.
Public fieldStatic memberSfCoverageThreshold
This bit will be set in the EventArgs of a Changed event every time the value returned by CoverageThreshold may have changed.
Public fieldStatic memberSfDistanceTolerance
This bit will be set in the EventArgs of a Changed event every time the value returned by DistanceTolerance may have changed.
Public fieldStatic memberSfEdgeAngleTolerance
This bit will be set in the EventArgs of a Changed event every time the value returned by EdgeAngleTolerance may have changed.
Public fieldStatic memberSfEdgeDetectionParams
This bit will be set in the EventArgs of a Changed event every time the value returned by EdgeDetectionParams may have changed.
Public fieldStatic memberSfExpectedLineNormal
This bit will be set in the EventArgs of a Changed event every time the value returned by ExpectedLineNormal may have changed.
Public fieldStatic memberSfFittingMode
This bit will be set in the EventArgs of a Changed event every time the value returned by FittingMode may have changed.
Public fieldStatic memberSfLengthThreshold
This bit will be set in the EventArgs of a Changed event every time the value returned by LengthThreshold may have changed.
Public fieldStatic memberSfLineAngleTolerance
This bit will be set in the EventArgs of a Changed event every time the value returned by LineAngleTolerance may have changed.
Public fieldStatic memberSfMaxNumLines
This bit will be set in the EventArgs of a Changed event every time the value returned by MaxNumLines may have changed.
Protected fieldStatic memberSfNextSf
Next state flag to be used in derived classes.
Public fieldStatic memberSfPolarity
This bit will be set in the EventArgs of a Changed event every time the value returned by Polarity may have changed.
Public fieldStatic memberSfRegionMode
This bit will be set in the EventArgs of a Changed event every time the value returned by RegionMode may have changed.
Public fieldStatic memberSfTimeout
This bit will be set in the EventArgs of a Changed event every time the value returned by Timeout may have changed.
Public fieldStatic memberSfTimeoutEnabled
This bit will be set in the EventArgs of a Changed event every time the value returned by TimeoutEnabled may have changed.
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Properties

  NameDescription
Public propertyAssurance
Gets or sets the tradeoff between speed and reliability when FittingMode is set to RANSAC mode.
Public propertyChangedEventSuspended
If nonzero, indicates that the raising of the Changed event has been suspended. This value is incremented when SuspendChangedEvent is called and decremented when ResumeAndRaiseChangedEvent is called.
(Inherited from CogSerializableChangedEventBase.)
Public propertyCoverageThreshold
Gets or sets the minimum acceptable proportion of inliers relative to the number of intersected projection regions. Line segments must meet this constraint to become results.
Public propertyDistanceTolerance
Gets or sets the maximum allowable distance between a line and an inlier of the line. Edge points must meet this constraint to become inliers of the line.
Public propertyEdgeAngleTolerance
Gets or sets the maximum allowable angle between a line and an inlier of the line. Edge points must meet this constraint to become inliers of the line.
Public propertyEdgeDetectionParams
Gets or sets the parameters for generating edge points from image data.
Public propertyExpectedLineNormal
Gets or sets the expected line orientation.
Public propertyFittingMode
Gets or sets the method to use when generating candidate lines. If you select Exhaustive mode, a candidate line will be generated for every possible pair of edge points. If you select RANSAC mode, a candidate line will be generated from a smaller number of randomly chosen point pairs.
Public propertyHasChanged (Inherited from CogSerializableChangedEventBase.)
Public propertyLengthThreshold
Gets or sets the minimum acceptable length of a line segment. Line segments must meet this constraint to become results.
Public propertyLineAngleTolerance
Gets or sets the maximum allowable angle between the normal of a line and the ExpectedLineNormal value. Lines must meet this constraint to become results.
Public propertyMaxNumLines
Gets or sets the maximum number of lines to be found. A LineMaxMulti license must be available to execute the tool with MaxNumLines set to greater than or equal to 0.
Public propertyPolarity
Gets or sets the polarity constraint. Edge points must meet this constraint to become inliers.
Public propertyRegionMode
Gets or sets the technique, PixelAlignedBoundingBoxAdjustMask or PixelAlignedBoundingBox, used to apply the region to the inspection image.
Public propertyStateFlags
Returns the complete set of state flags supported on this object. The flags may be indexed by name as shown in the following C# code snippet: if (changedObject.StateFlags["Color"] & eventArgs.StateFlags) { ... }
(Inherited from CogSerializableChangedEventBase.)
Public propertyTimeout
Gets or sets the maximum amount of time that the inspection is allowed to execute.
Public propertyTimeoutEnabled
Get or set the applicability of Timeout.
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Events

  NameDescription
Public eventChanged
This event is raised when one or more parts of the object's state may have changed.
(Inherited from CogSerializableChangedEventBase.)
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Remarks

Line finding is accomplished in two phases. The first phase, edge detection, finds edge points within the image(s). The second phase, line fitting, creates lines from roughly collinear subsets of the found edge points.

The first phase, edge detection, finds edge points within the image(s) using parameters defined in the CogLineMaxEdgeDetectionParams class. First, the input image is smoothed and decimated, using GradientKernelSizeInPixels. Gradient vectors are then computed for each pixel in the decimated image. Both the gradient vectors and the input image are projected over many caliper-like projection regions, using ProjectionLengthInPixels. A pixel is considered a candidate edge point if its projected gradient magnitude exceeds ContrastThreshold and if the ratio of its projected gradient magnitude and its intensity exceeds NormalizedContrastThreshold.

Only edge points with gradient directions sufficiently consistent with ExpectedLineNormal can possibly constitute the expected lines at the angle ExpectedLineNormal (where the gradient direction consistency is determined by LineAngleTolerance and EdgeAngleTolerance). Therefore, only such edge points are included in the line fitting phase. Edge points with inconsistent gradient directions are excluded from the line fitting phase and placed into the UnconsideredOutliers collection.

The second phase, line fitting, creates lines from roughly collinear subsets of the found edge points, using parameters defined in the CogLineMax class. Lines are evaluated using a RANSAC or an Exhaustive point selection methodology, depending on the FittingMode setting. Under RANSAC mode, the user may adjust Assurance to fit the desired result optimality and operation speed.

Line fitting is performed by iteratively evaluating candidate lines created from the found edge points. During each iteration two points are randomly selected from the found edge points, a candidate line is modeled from the selected points, and the candidate line inliers are determined.

An edge point is assigned to the inlier list of a candidate line only if it is in the proximity of the candidate line (determined by DistanceTolerance) and if its gradient direction is consistent with the angle of the candidate line (determined by EdgeAngleTolerance). Each edge point can only be assigned to the inlier list of a single line and each line is only allowed to contain at most one edge point from each projection region.

When the RANSAC iterations reach the maximum, the inliers of the best found line candidate will be identified. Then the found line will be refined using a least squares regression fit to the inliers, and the set of inliers will be re-evaluated using the refined line. The refinement will be repeated a maximum of three times until the number of inliers ceases to further increase.

Any edge points that are not inliers of the found line are placed into the ConsideredOutliers collection.

See Also