Number of input and output field

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

This transformation function is used to calculate similarity of an image and image-reference file . 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 has two parameters : 'key point descriptor method' to describe feature in an image and image-reference file.

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..