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Polarity Property
Polarity Property
Applies To
Vision Objects: Blob, Edge, ImageOp
Description
For Blob and ImageOp objects, Polarity defines the differentiation between objects and background.
For Edge objects, Polarity defines the transition of an edge.
Usage
VGet Sequence.Object.Polarity, var
VSet Sequence.Object.Polarity, value
Sequence Name of a sequence or string variable containing a sequence name.
Object Name of an object or string variable containing an object name. The object must exist in the
specified sequence.
var Integer variable that will contain the value of the property.
value Integer expression for the new value of the property.
Values
Edge: 1 - LightToDark Searching for an Edge transition from light to dark
2 - DarkToLight Searching for an Edge transition from dark to light
Blob: 1 - DarkOnLight Find a dark blob on a light background
2 - LightOnDark Find a light blob on a dark background
ImageOp: 1 - DarkOnLight The operation will be performed on dark objects.
2 - LightOnDark The operation will be performed on light objects.
Default: 1
Remarks
The Polarity property is important for both the Edge and Blob objects because it defines one of the core
parameters for each.
In the case of the Edge object, the Polarity defines the edge transition along the direction of the edge search.
When using the Blob object, Polarity is critical. The Vision System must be told whether or not to look for
light objects on a dark background or dark objects on a light background. Without the proper setting for
the Polarity property, the Blob object will return strange results. Keep in mind that if a Blob object can
find a dark object on a light background it can also find a light object on a dark background. The
ThresholdHigh property and ThresholdLow property will also have an impact on the Blob object 's ability
to find blobs. Please refer to ThresholdHigh Property and ThresholdLow Property for more information.
See Also
Blob Object, Direction Property, Edge Object, Object Tab, ThresholdLow Property, ThresholdHigh
Property
112 Vision Guide 5.0 Reference (Ver.5.3) Rev.1