Polarity property – Epson 5 User Manual

Page 126

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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.