ThresholdHigh Property

Applies To
Vision Objects: Blob, Contour, ImageOp, DefectFinder

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 value or expression for the new value of the property.

Values
1 to 255

This value must be greater than the ThresholdLow value or an error will occur.

Default: 128

Remarks
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 1-DarkOnLight, then grey levels between ThesholdLow and ThresholdHigh will be changed to black pixels and all other pixels will be white.

If the Polarity property is set to 2-LightOnDark, then grey levels between ThesholdLow and ThresholdHigh will be 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, Contour Object, DefectFinder Object, ImageOp Object, Polarity Property, ThresholdLow Property