Number of input and output field

Number of input field	:	Two
Number of output field	:	One

This transformation function is used to calculate similarity of two images. The output is a number (interval [0.0, 1.0]) that represent the similarity between them. A number value of 0.0 means that the two images are completely different whereas a return value of 1.0 means that all key points in the first image are matched with second image.
This transformation function uses 'key point descriptor method' to describe feature in an image.

The key point descriptor methods are :

• SIFT
  (Scale Invariant Feature Transform) face-image descriptor.
• SURF
  (Speeded-Up Robust Features) face-image descriptor.
• BRIEF
  (Robust Independent Elementary Features) image descriptor
• ROOTSIFT
  (Normalized Scale Invariant Feature Transform) face-image descriptor..