Comment by account42
3 years ago
> The way jpegli handles XYB color in a JPEG image is by applying an ICC color profile that maps the existing JPEG color channels to XYB.
That sounds like it might negatively affect compatibility with older decoders that do not handle color spaces correctly.
Jpegli has the possibility of using XYB. By default as by being just a replacement of mozjpeg or libjpeg-turbo it doesn't.
I believe Jon has compared jpegli without XYB. If you turn XYB on, you get about 10 % more compression.
Jpegli is great even without XYB. It has many other methods for success (largely copied over from JPEG XL adaptive quantization heuristics, more precise intermediate calculations, as well as the guetzli method for variable dead-zone quantization).
disclaimer: I created the XYB colorspace, most of the JPEG XL VarDCT quality-affecting heuristics, and scoped jpegli. Zoltan (from WOFF2/Brotli fame!) did the actual implementation and made it work so well.