Very interesting study. I’m shocked to see WebP and JPEG-XR perform so poorly on so many of the tests. Do they really perform *that* much *worse* than JPEG? It seems hard to imagine. I've done my own tests on jpeg, web-p and jpeg-xr by blindly comparing files of the same size and deciding subjectively which one I thought looked closest to the uncompressed version. The conclusions I came to were very close I thought to the RGB-SSIM tests which showed web-p best, with JPEG-XR much better than JPEG but significantly behind Web-P and JPEG much worse than all. This seemed consistent to me at all encoding qualities with many kind of images just as the RGB-SSIM tests show. It seems very curious that Y-SSIM, IW-SSIM and PSNR-HVS-M all show JPEG-XR and Web-P both dipping below JPEG quality at the same file sizes. I’d be very interested in seeing the images that those comparisons are determining JPEG-XR and Web-P are doing a worse job than JPEG.
I think the most important kind of comparison to do is a subjective blind test with real people. This is of course produces less accurate results, but more meaningful ones. It doesn't really matter if a certain algorithm determines a certain codec produces less lossy images than another codec if actual humans looking at the compressed images don’t tend to feel the same way. All that matters in the end is if a codec does a good job of keeping the details that the human compressing and viewing the image thinks are important, not what various algorithms testing image quality think are important. Although it’s outside the scope of this study, I wonder what interest Mozilla is taking on image formats with more features being supported on the Web? Lossy + transparency seems like a particularly desirable one for games and certainly for web developers in general. RGB565 colour format support sounds like it could be useful for optimized WebGL applications. _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
