What Apps allow a user to join photos of arbitrary quantity and size? I was surprised this does not exist and am considering writing the App myself in response. How can you merge multiple photos into a new merged photo? 

Like:

Input


200x300 "A.jpeg"
200x500 "B.jpeg"
200x100 "C.jpeg"


Merged Output


200x900 "A+B+C.jpeg"


Thoughts? Do I need to go write this myself :)?
Option "Stitch" in Photo Grid app allows you to merge multiple photos (up to 9).