1.0: JPEG-XL compression speed

[simon]

Hello,
On windows (7 or 10) at least, reading JPEG-XL image is almost as fast as reading classical JPEG images. In contrast, writing of JPEG-XL images is very long, far longer than writing classical JPEG images. Obviously, the JPEG-XL compression process is more complex than the classical JPG process, but it can be performed in parallel on several threads to boost speed (through the parameter --num_threads= when using the cjxl.exe program). I have the feeling that the compression process is very long on XnviewMP because this parameter is set by default to a very low value (e.g. 0 or 1). There is an option to use "multiple CPU cores" in XnViewMP batch convert dialog, but this is ineffective for JPEG-XL images. I suggest either to set the thread number to a higher value by default (e.g. 4, which seems to be a good compromise, working even on old computers), or to add an option in the JPEG-XL dialog to let the user to choose the number of threads he/she wishes
Thanks
simon