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Mozilla

Mozilla Launches Improved JPEG Encoder

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Mozilla today announced the launch of the latest version of its mozjpeg image encoder for JPEG files. The new version is already being tested on facebook.com, and Facebook donated $60,000 to Mozilla to continue its work on this project.

When it comes to image formats on the web, PNG and JPEG are pretty much the only game in town. Over the years, firms like Microsoft and Google have released their own formats, but none of them caught on. Google now often uses its WebP format on its own sites for Chrome users, but it’s getting little traction outside of Mountain View.

Mozilla promises that version 2.0 of its encoder reduces the file size of both baseline and progressive JPEGs by about 5 percent on average. Depending on the image, that number can be significantly higher (up to 15 percent) or slightly lower. Unlike the first version, which only focused on progressive JPEGS, this new version also improves images saved in the baseline format.

Mozilla’s CTO Andreas Gal told that the organization found that WebP, Microsoft’s JPEG XR and similar royalty-free formats don’t offer enough improvements over JPEG to justify the cost of adding a new image format to the Web. If that’s the case, then Mozilla’s time is best spent in trying to improve the encoding of what is already the most popular lossy compression format on the web.

For Facebook and other image-heavy sites  smaller file sizes mean it can render sites faster and shave off a few dollars from its bandwidth bill, so it’s no surprise the company is interested in this project.

“Facebook supports the work Mozilla has done in building a JPEG encoder that can create smaller JPEGs without compromising the visual quality of photos,” said Stacy Kerkela, software engineering manager at Facebook in a statement today. “We look forward to seeing the potential benefits mozjpeg 2.0 might bring in optimizing images and creating an improved experience for people to share and connect on Facebook.”

As Mozilla promised when it first launched mozjpeg earlier this year, the new version makes use of trellis quantization, a compression algorithm that has traditionally been used by video encoders. Other improvements include support for JPEG input, so it’s easier to re-compress existing images and a number of smaller changes that improve compatibility with existing JPEG decoders.

Mozilla is in a position where its support for a new format could put quite a bit weight behind it. To clear this hurdle, though, a new format would have to offer a significant improvement over the existing ones. Gal admitted that formats like WebP offer a number of other features that aren’t available in JPEG (like animations), but for Mozilla, that hasn’t been enough to support it yet. He does, however, believe that some of the newer formats will offer significant improvements. The problem with many of those is that they are encumbered by patents so it may be a while before we will see Mozilla support those (if ever). Instead, the format he seems to think has the largest potential to be included in Firefox is Daala, a new video compression technology (with applications for images as well), that Mozilla is working on in partnership with the Xiph.Org foundation.