Hi and welcome...
Unfortunately I can't help you in this matter, but what about VampyreImaging LIB? The Library can
handle APNG, so maybe there are ready procedures...
Or did you take a look at this
https://sourceforge.net/projects/apn...bpng/examples/?
There are some code examples... or you have to check C/C++ or Java examples ... something like that.
EDIT:
Here is a dissassembler for APNG (SRC)
https://sourceforge.net/projects/apngdis/files/2.8/
Looks like C-Code (VS2013)...