Lepton image compression: saving 22% losslessly from images at 15MB/s

#1

Post by samber » Thu, Jul 14, 2016, 2:21 PM UTC

Lepton image compression: saving 22% losslessly from images at 15MB/s
blogs.dropbox.com

Re: Lepton image compression: saving 22% losslessly from images at 15MB/s

#2

Post by deegles » Thu, Jul 14, 2016, 4:07 PM UTC

Does Dropbox do block or file-level deduping?

Re: Lepton image compression: saving 22% losslessly from images at 15MB/s

#3

Post by mbreese » Thu, Jul 14, 2016, 4:15 PM UTC

So, am I to read this as to mean that when I send Dropbox a JPEG, they are behind the scenes further compressing it using Lepton? Then when I request it back, they are re-converting it back to JPEG?

Re: Lepton image compression: saving 22% losslessly from images at 15MB/s

#4

Post by Klasiaster » Thu, Jul 14, 2016, 4:18 PM UTC

A similar approach has also been developed for use with zpaq, a compression format which stores the decompression algorithm as bytecode in the archive:

[The configuration] "jpg_test2" by Jan Ondrus compresses JPEG images (which are already compressed) by an additional 15%. It uses a preprocessor that expands Huffman codes to whole bytes, followed by context modeling. http://mattmahoney.net/dc/zpaqutil.html

Re: Lepton image compression: saving 22% losslessly from images at 15MB/s

#5

Post by daniel_rh » Thu, Jul 14, 2016, 4:19 PM UTC

mbreese wrote: post #3

So, am I to read this as to mean that when I send Dropbox a JPEG, they are behind the scenes further compressing it using Lepton? Then when I request it back, they are re-converting it back to JPEG?

That's the idea behind the algorithm, yes. And since it's lossless, every original bit is preserved. The same idea could be applied on the Desktop client instead of on the server, which would save 22% of the bandwidth as well and make syncing faster.