The Firefox developer tested Google's WebP image format on a variety of images but found a different alternative showed the best image quality improvements over JPEG.
Bad news for fans of Google's WebP: Mozilla has given it a resounding meh in a study comparing it and rival image formats.
The study compared JPEG to WebP, JPEG XR, and HEVC-MSP, a still-image format drawn from the new HEVC/H.265 video compression technology. Google has touted WebP as a way to reduce file sizes on the Web and therefore to speed up Web page loading and cut bandwidth costs.
Firefox developers initially decided against WebP, but the support of significant sites, including Facebook, encouraged Mozilla to reevaluate. The study doesn't seem to have carried the day, though.
"We consider this study to be inconclusive when it comes to the question of whether WebP and/or JPEG XR outperform JPEG by any significant margin," Mozilla programmer Josh Aas said in a blog post Thursday. Indeed, it was the HEVC-MSP that showed the biggest improvement over JPEG.
But even if Mozilla didn't get excited by WebP, it didn't reject it, either. "We are not rejecting the possibility of including support for any format in this study on the basis of the study's results. We will continue to evaluate the formats by other means and will take any feedback we receive from these results into account," Aas said, pointing people to a discussion about Mozilla's findings.
The study compared the file size of several collections of images when compressed with the various formats, using four different signal-processing calculations to measure quality.
It didn't evaluate various other WebP factors, such as its ability to include transparent "alpha" channels, which JPEG lacks, and its ability to handle losslessly compressed images, which means it can substitute for the PNG file format, too.