HDR images appear dark and dull about pdn-jpegxl

[0xC0000054]

That HDR image is 16-bits-per-channel. GIMP natively supports 16 and 32 bits-per-channel images.
I am not sure what the other applications do when loading it.

I do not think that I have any control over this. The plugin tells libjxl that it wants 8-bits-per-channel output, and libjxl provides it.
How libjxl converts HDR data to 8-bits-per-channel is a question for the libjxl repository.

[o-l-a-v]

I did some testing with djxl, latest build from here:

• https://artifacts.lucaversari.it/libjxl/libjxl/latest/

djxl.exe reported its' version as djxl v0.9.0 96d76a3.

I used jxlinfo.exe .\..\input.jxl, it said:

JPEG XL file format container (ISO/IEC 18181-2)
JPEG XL image, 1638x2048, lossy, 16-bit RGB
Color space: RGB, D65, Rec.2100 primaries, PQ transfer function, rendering intent: Perceptual
Uncompressed Exif metadata: 818 bytes
Brotli-compressed XML  metadata: 5664 compressed bytes
unknown box: type: "hrgm" size: 147802
layer: full image size, name: "main"

It says "Rec.2100" so I first tried with --color_space=RGB_D65_202_Per_PeQ --bits_per_sample=8 but it did not produce expected results. I then opened the JXL file in GIMP and looked at the metadata, it said Exif.Photo.ColorSpace: sRGB, which led me tro try the following:

• djxl .\..\input.jxl .\..\out.png --bits_per_sample=8 --color_space=RGB_D65_SRG_Per_SRG

It created something that looks very close to the reference JPG image, also when opening it in in Paint.NET.

Here is the output PNG from above command:

Click to expand

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Assumption: djxl can produce results that looks alright in Paint.NET, but then one have to feed it what color space to use?