XnView Software

I'm on a M1 Pro mac and have to say the performance of viewing jp2 files in XnView is very slow compared to other alternatives. I'd say it's 3-4x slower on large images compared to e.g. Phoenix Slides, which is open source. Some optimisations would be very welcome.

XnView MP uses OpenJPEG, but i think that Phoenix Slides uses internal macos codec

xnview wrote: Fri Apr 12, 2024 9:45 am XnView MP uses OpenJPEG, but i think that Phoenix Slides uses internal macos codec

Ok. Phoenix Slides does seem slightly faster than the built-in macos preview app, though.

I've done some more comparisions, and it's not just Jpeg2000 that's remarkably faster, but also decoding large jpeg and jpeg-xl images.
The ultimate image viewer would have the functionality of XnView and the speed of Phoenix Slides

I checked, and ultimately Phoenix uses CGImageSourceCreateWithData, the main MacOS image decoding API, which is very optimized and GPU accelerated. While XnView normally only uses built-in code, it's not impossible that it could interface with MacOS's API... just doesn't seem likely, especially without a testing environment.

Maybe if QT ever natively supports it?

Right with internal decoder loading is 2 times faster. See issue for current status and some details.

This problem is supposed to be fixed in XnView MP 1.8.4. Please check and confirm the bug fix here.