Jpegli, a new JPEG coding library, does bring a significant compression ratio improvement, comparing to libjpeg-turbo and MozJPEG.
I selected 332 lossless non-photographic PNG images for some rough tests, on macOS Sonoma 14.4.1. The images were recorded after applied with ImageOptim‘s lossless optimisation for the minimal possible sizes, and Jpegli was directly from libjxl version 0.10.2.
The built-in JPEG library (quality at 90, supposed to be libjpeg-turbo?) encoded them to 174,095,425 bytes, MozJPEG (quality at 91) encoded them to 145,553,618 bytes, and Jpegli (quality at 92) encoded them to 128,006,534 bytes. That is about 26.5% smaller than libjpeg-turbo and 12% smaller than MozJPEG.
The quality values were tested initially with some images based on DSSIM, and the bonus 1 of MozJPEG and bonus 2 of Jpegli also reflected the latest benchmark by Jon Sneyers.
For fun, I tested Jpegli with XYB (–xyb), and the size becomes 112,809,722 bytes— even 11.9% smaller than conventional Jpegli. However, some softwares displayed thumbnails of XYB JPEG files with totally wrong colours.
Even without XYB, Jpegli is still the most competitive choice for encoding JPEG images.
