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Yeah, I agree that webp looks better for many of the images. For most of them it comes back to the subjective issue that webp (and VP9) choose to err on the sid
by pavon 5y ago
Yeah, I agree that webp looks better for many of the images. For most of them it comes back to the subjective issue that webp (and VP9) choose to err on the side of blurring detail they can't encode, while jpeg XL (and x264, etc) try to keep all the detail they can at the expense of more artifacts. There are very vocal proponents of both approaches, and personally I think it varies by the image content.
For all these examples, I was comparing at Small (as with Tiny they were both bad enough but in different ways that I often couldn't decide which was least bad). For the Abandoned Factory and Panthera Tigres, I think the extra detail of JXL looks better than the blurring of WEBP. On the otherhand, I think WEBP looks cleaner than JXL for Buenos Aires, Reykjavik, B-24 Bombers without loosing significant detail. And Avenches is a mix as JXL looks much better than WEBP for the trees and tile roof, but has worse chroma artifacts near the edges of the hat and clothing.
But that isn't the whole story, as for some of the images WEBP seems to both preserve more detail, and have fewer artifacts, such as Air Force Academy Chapel, Pont de Quebec, Steinway and White Dunes. What all these cases seem to have in common is a smooth gradient adjacent to sharp detail. WEBP seems to do a much better job of dealing with that boundary by blurring the smooth part, put preserving the sharp lines.
And if you bump up to WEBP2, the number of cases where it both preserves more detail and has fewer artifacts than JXL increases significantly.
- astrange 5y ago> Yeah, I agree that webp looks better for many of the images. For most of them it comes back to the subjective issue that webp (and VP9) choose to err on the side of blurring detail they can't encode, while jpeg XL (and x264, etc) try to keep all the detail they can at the expense of more artifacts. There are very vocal proponents of both approaches, and personally I think it varies by the image content. In VP9/WebP this wasn't a "choice" so much as they were optimizing for good looking marketing graphs instead of pictures. You get blurry images if you target a metric like PSNR instead of actually looking at your output. x264 does have a few different tunings, the film one will try to turn detail to noise and the animation one won't.
- JyrkiAlakuijala 5y agoThe amount of artefacts should be substantially reduced in JPEG XL in the next round of comparisons. Last week I submitted the 'ac strategy decision tree traversal' change to libjxl, which reduces ringing artefacts substantially, often by 60-70 %. It does a diligent job by choosing the best combination of small integral transforms (there are 10 different 8x8 transforms) instead of just satisfying with a large transform. This change also improves on image quality, sharpness and truthfulness, it doesn't just blur the artefacts away.
- JyrkiAlakuijala 5y agoOn discord someone posted a before-after-original animations about last week's improvements in low-bpp JPEG XL compression for anime drawings: https://cdn.discordapp.com/attachments/852294618694942750/854459641056722944/jxl_patch_cmp_d1.webp https://cdn.discordapp.com/attachments/852294618694942750/85... This JPEG XL quality improvement has not yet landed in online comparison tools.