How to calculate image matching percentage in opencv offline Image Recognition?

edit

Hello sir/Madam, My project is about offline Signature Recognition and we have completed our work up to feature extraction part and now we have to find result of matched image in percentage that whether signature image is genuine or forgery. The result of matched image should be display from database of signature image. Is possible to calculate the percentage in OpenCV of signature image? And can we known total feature of image and from that how many has matched with our database signature image? So we are requesting you to reply us as early as possible.