Tried C++ to D. Wrong result.

[Dmitry]

I tried translate C++ programm to D, but result is different.

original:
https://github.com/urraka/alpha-bleeding/blob/master/src/alpha-bleeding.cpp
result (with removed alpha):
https://github.com/urraka/alpha-bleeding/blob/master/media/alpha-bleeding-opaque.png

my:
https://pastebin.com/GzZQ7WHt
result (with removed alpha):
https://www.dropbox.com/s/xbjphlievboslv2/original-2.png

What did I wrong?

P.S. Also on an one image it was crashed at line 63 (range 
violation)
https://pastebin.com/TenGusw0
so I added ((index + 3) < N) into condition.