Day 6A Villain Rises...
All is merry in Santa's Village, the standard mass-produced Elf Advent Calendar had a big chocolate today and the mood is electric. That is, until reports start flying in by MerryMail from Santa's outposts across the world that they've been receiving strange messages from a mysterious sender.
They seem to be very small cut-up fragments of a larger postcard. A note, sent directly to Santa himself, reads:
Dear Santa,
You've grown complacent. Grown sloppy. Sat watching the snowflakes, sipping your cocoa, you are BLIND to the world around you. It's time to wake up. And I HATE Christmas music.
I've descended on a city with a name you'd recognise, and I'm bringing eternal frost and a bitter cold with me!
Good luck finding me -- I've cut up my postcard into hundreds of pieces!
Cold regards, The Grinch.
This note is widely regarded to be a total vibe killer. The elves are terrified, and look to you for help...
There are 256 fragments of the postcard, that need to be stitched together in a 16x16 grid to reconstruct the original image.
Once you've stitched together the image, you can get the answer by performing the following:
pngtopnm image.png > image.pnm
md5sum image.pnm
The answer will be the outputted hex bytes.
Hint 1: the sample code is a good starting point.
Hint 2: chunk_964560701.png is the bottom-right chunk of the final image.
Hint 3: don't overcomplicate this, edge comparison is easier than you think!