Result on test data:

Link: http://flic.kr/p/dm8AyL

Result on our photos:

Link: http://flic.kr/p/dm8Ypu

This is the farthest we can go with homographies.

Link: http://flic.kr/p/dm8E77

All the requirements work well.

Extra Credit:

We implement a brightness balance algorithm. The basic idea is to calculate the difference between nearby pictures, and fix the new inserted picture with an average bright level.