Decoding jxl is much slower than equivalent png

[terranprog]

I am finding decoding jxl images using jxlatte takes around 10 times longer than decoding the same image saved as png.

My process is as follows:

1. Start with png image
2. Convert png to jxl using the reference jxl encoder libjxl. Use lossless compression.
3. Read png image using ImageIO
4. Read jxl using jxlatte with default settings

I did 3 runs of each (with JVM warmup) Times are in milliseconds.

JXL Time to process 20 jxl files is 4004 Time to process 20 jxl files is 3919 Time to process 20 jxl files is 3882

PNG Time to process 20 png files is 362 Time to process 20 png files is 398 Time to process 20 png files is 379

• Are there any options in jxlatte that will speed up the decoding process?
• Are there any different settings I can use when encoding the jxl that will create images that can be decoded faster?
• Is there scope or plans for improving the decoding time in jxlatte? Or is it already heavily optimised?

I have attached a sample jxl file

Sample.zip

[terranprog]

I have raised a pull request with some simple code changes that improve performance.

https://github.com/Traneptora/jxlatte/pull/25

[Traneptora]

jxlatte isn't optimized, for starters, but also do note that I've been focusing on compliance and completeness recently and fixing bugs rather than optimizing.

[terranprog]

OK thanks. That's good to hear. Being new to jpegxl format, I wasn't sure if this was an inherent trade-off with the format.

[Traneptora]

It is, since PNG is much less sophisticated, but it's nowhere near as extreme as you'd see with jxlatte vs standard PNG.