Feature request: Support new PNG cICP chunk

[kmilos]

These carry color space information and extend iCCP, defined in latest extensions incorporated into the spec: https://w3c.github.io/PNG-spec/

There seems to also be an iCCN chunk, see also https://github.com/w3c/ColorWeb-CG/blob/master/hdr-in-png-requirements.md#decoder (TBC if it is part of the spec).

[svgeesus]

The official specification for cICP. cICP is now implemented in the Chrome browser, DarkTable, and Adobe PhotoShop. The four fields have the exact same meanings as in ITU-T-H.273.

iCCN was dropped, as it added only two features:

• support for ICC v4 profiles
• UTF-8 profile name

but everyone was already putting ICC v4 profiles inside iCCP so we corrected the ICC reference in the PNG spec to allow that instead.

[ProgramMax]

I want to clarify something here:
The original post is about adding support for the new cICP chunk (coding-independent code points). @svgeesus linked to the cICP chunk and mentioned how it works (the four fields). However, he said "iCCP" in the first few lines when he meant "cICP".

The older iCCP chunk (ICC Profile) was indeed updated to support ICC v4 profiles.

[svgeesus]

However, he said "iCCP" in the first few lines when he meant "cICP".

Whoops, corrected!