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ThresholdHigh Property
ThresholdHigh Property
Applies To
Vision Objects: Blob, ImageOp
Description
Sets or returns the ThresholdHigh value for a Blob or ImageOp object.
Usage
VGet Sequence.Object.ThresholdHigh, var
VSet Sequence.Object.ThresholdHigh, 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
1 - 255 This value must be greater than the ThresholdLow value or an error will occur.
Remarks
Blob Objects:
The ThresholdHigh property works with the ThresholdLow property to define the grey level regions which
represent the feature (or object), the background and the edges of the image. The ThresholdHigh property
defines the upper bound for grey level values that are considered to be a blob. Any part of the image which
falls within grey level region between ThresholdLow and ThresholdHigh will be assigned a pixel weight of
1. (i.e. it is a blob.)
If the Polarity property is set to DarkOnLight, then grey levels between ThesholdLow and ThresholdHigh
will changed to black pixels and all other pixels will be white.
If the Polarity property is set to LightOnDark, then grey levels between ThesholdLow and ThresholdHigh
will changed to white pixels and all other pixels will be black.
One of the problems regarding the ThresholdLow and ThresholdHigh Properties is finding the correct
values to use for each. This is where the Histogram feature of Vision Guide comes in. You can run a
Histogram on an image to see the relationship between the pixel counts at various grey levels. From the
Histogram dialog, you can adjust each of the threshold values and view the results.
See Also
Blob Object, ImageOp Object,Object Tab, Polarity Property, ThresholdLow Property
172 Vision Guide 5.0 Reference (Ver.5.3) Rev.1