Add support for APNG chunks

rayrobdod / png-inflate

A clean filter for git that decompresses png images

Apache License 2.0

2 stars 0 forks source link

Add support for APNG chunks #2

Closed rayrobdod closed 4 months ago

rayrobdod commented 4 years ago

APNG is an extension to PNG adding several non-standard chunks (although the current w3c editor's draft of the PNG spec mentions the APNG chunks)

Check which APNG chunks have compressed parts
Check whether the APNG chunks that do not have compressed parts are safe to copy, either marked as such or would be safe for this algorithm to copy
Figure out how to check whether two APNG files have the same semantics

rayrobdod commented 3 years ago

https://wiki.mozilla.org/APNG_Specification

acTL and fcTL have no compressed parts. fdAT is a u32 followed by a compressed data chunk.

rayrobdod commented 2 years ago

fdAT chunks for the same frame (between the same two fcTL chunks) can be combined, like how IDAT chunks can be combined, but doing so would require changing the sequence number of following APNG chunks to account for the reduced number of APNG chunks.

rayrobdod commented 4 months ago

fd3549d20f2d679b308ef92ed550b92540f6a0d2