32-bit HDR PNG support added

[Ash]

Apps: All
Platforms: Windows, macOS and iPad

All Affinity apps now support import and export of 32bit HDR PNG files, as described in the PNG specification (3rd edition). Both PQ and HLG are supported alongside full / narrow range and a full set of primaries. Files exported can be used directly in video editing applications or shared on the web (Chrome now supports HDR PNG files). In addition, legacy PNG and TIFF files exported from Photoshop with CICP data embedded in an ICC profile are also able to be imported.

 

[MikeTO]

Incredibly trivial, but in the 2.4 feature list announcement, PNG Third Edition is spelled Addition.

 

[NotMyFault]

I would love to see the ability to export PNG above 32767 pixel count in x/y direction.

The current limit is very unfortunate. All pNG above 32767 will get silently downscaled.

[NotMyFault]

I Exported a test file having SRGB linear profile without embedding the profile, using ICC profile from document 

The export PNG shows a different profile BTU 2100. This seems like a bug.

[ashf]

I didn't know that PNG has HDR mode.
Just wondering how many people are using it?
Can't PNG be replaced with JPEG XL?

[Affinityconfusesme]

I have never heard of this format either.

[James Ritson]

13 hours ago, ashf said:

I didn't know that PNG has HDR mode.
Just wondering how many people are using it?
Can't PNG be replaced with JPEG XL?

It was introduced last year: https://www.w3.org/TR/png-3/

So far, FCPX and Davinci Resolve appear to support this (I haven't tried other editors yet), as well as macOS Sonoma and various web browsers, so it's getting fairly decent adoption. It looks to be a good solution for interchanging HDR broadcast imagery in a lossless format. OpenEXR is supported by most NLEs but has non-user-friendly colour management.

JPEG-XL was possibly going to be a good solution, but Chrome dropped it (not long before/after we released V2, I think) and support for it isn't widespread.

The cICP chunk in this PNG format allows the image to be tagged and processed with various video-centric colour spaces, which is more robust for broadcast workflows where the imagery needs to integrate seamlessly with video content, rather than being dependent on ICC (particularly for HDR content where you have HLG/PQ colour spaces with different transfer characteristics).

[Graphite Addict]

I'm certain this new feature will be useful to someone but now my PNG exports from Designer have muddy, subdued colours!

What was the previous default PNG setting prior to 2.4 please?

*Edit: Primaries: BT.709 and Transfer Function: BT.709 appear to give me the same colours as I see on screen before export. I am unsure if this was the previous default as I have no idea what either of these settings are and the Affinity Designer Help files do not explain it in a way that someone who didn't already know the answer could decipher*

Finding information about the new PNGs online is a circular loop that mostly bring me back here. If the new PNG format is that obscure, having it be the new default was a poor choice.

Edited February 29 by Graphite Addict
BT.709 seems to do the trick

[Chris B]

Hey @Graphite Addict The preset of PNG or PNG Dithered should be fine. None of the HDR stuff goes out on 8bit formats so as long as you've got either of those presets selected, it should be fine. If that isn't true, we may need a copy of the file to investigate.

[Frozen Death Knight]

I have a question about this feature. I tried exporting an image with HDR. However, what I noticed was that viewing the exported image outside of Affinity made the colours more dull and less bright when using the built in Photo viewer on Windows 10. When importing the new .png-file back into Affinity the colours are correct again with the HDR preview on. Any ideas why this is?

Also, I just noticed that the Export window with the preview of the final image doesn't support HDR previewing, even when I have HDR enabled in the Windows 10 settings.

[Chris B]

Hey Frozen Death Knight

On 3/1/2024 at 3:09 PM, Frozen Death Knight said:

When importing the new .png-file back into Affinity the colours are correct again with the HDR preview on. Any ideas why this is?

I assume Windows Photo Viewer doesn't support the view? The file outputs would normally be intended for something like Final Cut Pro or similar. Even Photoshop displays the HDR PNG washed out.

Have you seen James' video on this?

As for the Export Preview, It doesn't yet support a 32-bit preview. These are lossless outputs so you won't need to be zooming in looking for compression artifacts but I do think we should be showing an accurate 32-bit preview. There is probably already a log of this so I'll do some digging.

[James Ritson]

On 3/1/2024 at 3:09 PM, Frozen Death Knight said:

I have a question about this feature. I tried exporting an image with HDR. However, what I noticed was that viewing the exported image outside of Affinity made the colours more dull and less bright when using the built in Photo viewer on Windows 10. When importing the new .png-file back into Affinity the colours are correct again with the HDR preview on. Any ideas why this is?

This result could be that Windows 10 is tone mapping the HDR values to SDR, or it's falling back down the list of chunks in the metadata (the HDR signalling is contained in the cICP chunk, but if the decoder doesn't support the cICP or iCCN chunks it should use sRGB, iCCP, gAMA/cHRM in that order). I wonder if it's the latter, as the bright highlights on the shield don't look sufficiently tone mapped and are still slightly blown out.

Did you screenshot the Windows photo viewer to post it here? That could add another layer of colour management that prevents us from seeing the exact result you're describing. That said, if the PNG imports fine back into Affinity Photo then the HDR pixel values and chunks signalling the transfer function and colour space are in-tact. You might get the intended result if you import the PNG into something like an NLE that supports HDR display mapping (perhaps Davinci Resolve?)