FriedemannJun 24
Chris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿

The Third Edition of Portable Network Graphics (PNG) today became a W3C Standard.

It adds support for High Dynamic Range (HDR), and adds Animated PNG to the official standard.

https://www.w3.org/TR/png-3/

Portable Network Graphics (PNG) Specification (Third Edition)

This document describes PNG (Portable Network Graphics), an extensible file format for the lossless, portable, well-compressed storage of static and animated raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, greyscale, and truecolor images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits.

Jun 24 at 1:16pmWeb
Show threadChris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿Jun 24

Chris Blume, who chairs the PNG Working Group, explains why this is important

https://www.programmax.net/articles/png-is-back/index.html

PNG is back!

After 20 years, PNG is back with renewed vigor! A new PNG spec was just released.

Show threadChris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿Jun 24

One of the new features is CICP, a new way to compactly label the SDR or HDR color space.

I did a deep dive on how this works and how to use it

https://svgees.us/blog/cICP.html

cICP in PNG, explained • Chris Lilley

Show threadManuel BabolinJun 27
@svgeesus Awesome article Chris! 👏
I noticed that the test image also displays correctly in Photoshop, macOS and iOS. I didn't think they were ready to read CICPs yet! Hopefully Adobe will add the ability to export images with CICP soon.
Show threadChris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿Jun 27
@manuelbabolin Thanks!
MacOS and iOS seem to have system-level support for CICP, which apps like Safari and Photoshop can draw on.
Show threadManuel BabolinJun 29

@svgeesus I did some tests with an image that uses cICP to label the Display P3 color space. I looked at the info on macOS, Photoshop and Affinity.

macOS: Display P3
Photoshop: image P3 (8bpc)
Affinity: RGBA/32 (HDR) - P3 D65 (Linear)

Photoshop puzzles me 🤔

Show threadChris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿Jun 24

The W3C PNG Working Group has documented the (very good) level of implementation of the Third Edition

https://w3c.github.io/png/Implementation_Report_3e/

Show threadHiddeJun 24
@svgeesus congrats!
Show threadGraham Sutherland / PolynomialJun 24
@svgeesus nice! looking forward to being able to store PQ quantised images losslessly this way ^^
Show threadChris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿Jun 24

@gsuberland yes, both BT.2100 PQ and P3D65 PQ are supported

We also support Content Light Level (MaxFALL, MaxCLL) and Mastering Display Color Volume.

Show threadGraham Sutherland / PolynomialJun 24
@svgeesus is P3D65 PQ a different transfer curve? I always thought it was mathematically identical to the BT.2100 PQ curve, although admittedly I never looked at the P3 stuff very hard.
Show threadChris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿Jun 24
@gsuberland Same curve, different primaries
Show threadGraham Sutherland / PolynomialJun 24
@svgeesus ah, yeah, makes sense.
Show threadChris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿Jun 24

@gsuberland I blogged about that, today

https://svgees.us/blog/cICP.html#introducing-cicp

cICP in PNG, explained • Chris Lilley

Show threadGraham Sutherland / PolynomialJun 24
@svgeesus /cc @QuaternionCats
Show threadTALJun 25
@svgeesus could it add explicit support for alt text?
(sorry if this is a stupid question, a "find" on the spec page didn't return anything)
Show threadChris Lilley 🏴󠁧󠁢󠁳󠁣󠁴󠁿Jun 25
@tal Alternative text for an image typically depends on the context; the same image can be used for different purposes. Which is why it lives in the document, not the graphic.
Show threadTALJun 25
@svgeesus Understood, thanks. I presume I'm going over old ground here, but I'd rather alt text in the image as a fallback for when the document writer forgets.