ledoge / jxr_to_avif

HDR JPEG-XR -> AVIF converter

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About

This is a simple command line tool for converting HDR JPEG-XR files, such as Windows HDR screenshots, to AVIF.

The output format is hardcoded to be 12 bit 4:4:4 for maximum quality. Unfortunately, these files cannot be decoded natively by Windows's AV1 extension, as it only seems to do 8 bit up to 4:4:4 or 10/12 bit up to 4:2:0. However, the files open fine in Chromium.

Usage

jxr_to_avif [--speed n] input.jxr [output.avif]

HDR metadata

The MaxCLL value is calculated almost identically to HDR + WCG Image Viewer by taking the light level of the 99.99 percentile brightest pixel. This is an underestimate of the "real" MaxCLL value calculated according to H.274, so it technically causes some clipping when tone mapping. However, following the spec can lead to a much higher MaxCLL value, which causes e.g. Chromium's tone mapping to significantly dim the entire image, so this trade-off seems to be worth it.

jxr_to_avif's Issues

Works great, but some details get lost on conversion

Overall it looks great, but some highlights get lost on conversion. Here is an example where the red lines in the background lose highlights and detail.

Is it possible to build in Linux?

It seems the application can only run in Windows.

feat: Reverse conversion

Windows will get HDR Desktop backgrounds soon, but sadly only JXR, because... Microsoft I guess... so it would be really nice to have support for the reverse conversion as you can already get HDR images using AVIF for example to get pictures from Movies or some cameras (via RAW) and maybe soon from android phones (via Ultra HDR) and being able to set those as desktop backgrounds would be really cool.

wrong pixel format

I'm trying to convert a JXR screenshot made with nvidia shadowplay screencap feature, but as i type the command
.\jxr_to_avif.exe '.\Red Dead Redemption 2 Screenshot 2024.01.14 - 16.09.17.53.jxr' reddead.avif it prints out the error "Wrong pixel format"