Just use Flash Tool to re-lock back - http://www.flashtool.net/
By the way, you already unlock, no point you re-lock back, it still warranty void and Bravia Engine 2 / X-Reality won't coming back for photo view in album even you re-lock back.
The Bravia Engine 2 / X-Reality only can remain if you had backup TA before, but since now the only root need unlocked the bootloader 1st, which means you can't do TA backup anymore as TA backup do need root access on device that never unlocked the bootloader for it.
Phone: Redmi Note & HTC ONE (M8) | ROM: Stock (Redmi) & Android Revolution HD 10.2 (M8)
Future Phone: Xiaomi Mi4
Ex. Phone: Nokia 3310, Samsung S500, Nokia 7610, 7270, 7280, SE K750, Nokia N73, LG Viewty KU990, Samsung Pixon, UltraTOUCH, OMNIA II, Nokia 3120 Classic, Google Nexus One, Samsung Galaxy S II, S III, Sony Xperia Z, Z Ultra, Samsung Galaxy Note 3.
Tablet: Sony Xperia Tablet Z | ROM: Stock v10.5.A.0.230
Future Tablet: Still Finding
Ex. Tablet: Google Nexus 10