Home Spectral Descriptors Virtual Descriptors
See also: Background Information on Spectral Descriptors, Predefined Spectral Descriptors, Spectral Descriptor Editor, IGF Descriptor, How to Create Classifiers, Spectral Descriptor Generator, Programming with Spectral Descriptors 

Virtual Descriptors

In addition to the predefined descriptors Epina ImageLab supports "virtual descriptors" which are arithmetic combinations of several specified descriptors. In order to define a virtual descriptor you have to click the virtual descriptor button () and enter a simple mathematical formula based on the specified descriptors ("DCxxx"). The formula can contain the following operators:

+ (addition)
- (subtraction)
* (product)
/ division
abs (absolute value)
sqr (square)
sqrt (square root)
As an example, the following formula combines the descriptors DC001, DC004 and DC003 to give a new (virtual) descriptor: DC1*(DC4+DC3). Please note that the formula may use the descriptor identifiers without any leading zeros (i.e. "DC003" is equal to "DC3").

Hint: Please note that the formula specifying a virtual descriptor must not contain any references to other virtual descriptors; only predefined descriptors are allowed to be entered in the formula of the virtual descriptor. If the formula refers to a virtual descriptor, the virtual descriptor returns a zero value (without warning).