First define the parameters of the attractiveness, then select a suitable software/tool of image processing that deals all these parameters, then put a standard measure of the parameters of attractiveness for that software/tool. For that you can contact any computer scientist/Mathematician who deal with image processing......

Dear Subrata, easier said than done ;)

yeah i know its not so easy. but first  which factor of a face you think to be part of attractiveness?? Have you include complexion, shape and other factors of attractiveness? Attractiveness is a relative mater, one may seem to be attractive to some one and for some other one not. So its too hard to make a general model. But may be done with some absolute type of factors of face, absolute means almost similar to everyone.

Here are some articles on beauty.

https://www.technologyreview.com/s/426144/beauty-now-in-the-eye-of-the-algorithm/

https://services.open.xerox.com/WebApp2.svc/aesthetic-search/

https://medium.com/the-physics-arxiv-blog/the-algorithm-that-sees-beauty-in-photographic-portraits-435ab8064646

https://howhot.io/

https://www.technologyreview.com/s/537741/computational-aesthetics-algorithm-spots-beauty-that-humans-overlook/

http://medicalxpress.com/news/2015-10-beauty-eye.html

http://www.eurekalert.org/pub_releases/2009-12/uot-rdn121609.php

http://www.eurekalert.org/pub_releases/2006-05/uocp-bat050806.php

https://www.sciencedaily.com/releases/2007/10/071012143057.htm

http://www.eurekalert.org/pub_releases/2009-08/ps-wss082409.php

http://www.eurekalert.org/pub_releases/2008-11/uol-sff111808.php

http://www.eurekalert.org/pub_releases/2006-09/uoc--bat092606.php

http://www.eurekalert.org/pub_releases/2011-04/w-ibf040711.php

http://www.eurekalert.org/pub_releases/2007-11/plos-itb112007.php

http://www.ncbi.nlm.nih.gov/pubmed/18556905

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0021852

http://www.news-medical.net/news/2007/11/21/32797.aspx

http://phys.org/news/2006-06-software-beauty.html

http://onlinelibrary.wiley.com/doi/10.1111/j.2044-8295.2012.02114.x/full

Regards,

Joachim