Mozilla's JPEG compression slims down file sizes

Mozjpeg seeks to make image file sizes even smaller without a loss of quality

Mozilla has released an updated version of its JPEG compression tool that shaves down file sizes by 5 percent, a small figure but one that is significant for image-intensive Web services such as Facebook.

The tool, called mozjpeg 2.0, will ultimately "reduce page load times and ultimately create an enhanced user experience for sites hosting images," wrote Josh Aas, senior technology strategist for Mozilla on its blog.

Facebook has begun testing the tool and donated US$60,000 for its further development, Aas wrote.

The JPEG format has been in use for more than 20 years, and most images on the Internet are served in that format. It's a "lossy," or compressed image format, which aims to remove some data to reduce the file size but maintain the photo's integrity as much as possible.

On average, both baseline and progressive JPEG files are reduced by 5 percent by mozjpeg, Aas wrote. The previous iteration of mozjpeg only improved compression for progressive JPEGs, Aas wrote.

Mozjpeg is based on the libjpeg-turbo library, which is used for decoding JPEGs in Firefox. But mozjpeg does use more computing power than libjpeg-turbo when compressing, Aas wrote.

As a result, "we recommend using libjpeg-turbo for a standard JPEG library and any decoding tasks," he wrote. "Use mozjpeg when creating JPEGs for the Web."

Send news tips and comments to jeremy_kirk@idg.com. Follow me on Twitter: @jeremy_kirk

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