  We report on pairwise comparisons by human raters of JPEG images from libjpeg
and our new Guetzli encoder. Although both files are size-matched, 75% of
ratings are in favor of Guetzli. This implies the Butteraugli psychovisual
image similarity metric which guides Guetzli is reasonably close to human
perception at high quality levels. We provide access to the raw ratings and
source images for further analysis and study.
