Lepton - A new lossless image format from Dropbox for compressing JPEGs by ~22%

[Arthur]

Even though it is "old" news I thought it was quite interesting. Whenever you upload a JPEG to Dropbox they recompress the image into their new Lepton format (.lep) which are on average 22% smaller in size. When you download the JPEG from Dropbox they reverse the process.

 

A command-line converter (and third-party GUI) can be downloaded below. Since there aren't many (any?) image viewers that currently support the Lepton format it's probably not worth converting all of your JPEGs, but it might be a useful format for archival purposes.

 

Blog / Download (GUI frontend available here)

 

We are pleased to announce the open source release of Lepton, our new streaming image compression format, under the Apache license.

 

Lepton achieves a 22% savings reduction for existing JPEG images, by predicting coefficients in JPEG blocks and feeding those predictions as context into an arithmetic coder. Lepton preserves the original file bit-for-bit perfectly. It compresses JPEG files at a rate of 5 megabytes per second and decodes them back to the original bits at 15 megabytes per second, securely, deterministically, and in under 24 megabytes of memory.

 

We have used Lepton to encode 16 billion images saved to Dropbox, and are rapidly recoding our older images. Lepton has already saved Dropbox multiple petabytes of space.

 

Community participation and improvement to this new compression algorithm is welcome and encouraged!

 

Edited December 6, 2016 by Arthur