Lepton image compression

**Sportman** · 15th July 2016, 00:55

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:

https://blogs.dropbox.com/tech/2016/...ages-at-15mbs/

https://github.com/dropbox/lepton

**SvenBent** · 15th July 2016, 01:18

This is kind of a PackJPG alternative ?

**dado023** · 15th July 2016, 02:41

@SvenBent

that was my first thought as well.
I wonder is it, and how much better than PackJPG.

**Shelwien** · 15th July 2016, 05:29

http://nishi.dreamhosters.com/u/lepton20160715.exe

"Copyright (c) 2006...2016, Matthias Stirner and HTW Aalen University"

**SvenBent** · 15th July 2016, 06:33

Code:

D:\Comics>lepton20160715.exe oots1039.jpg
lepton v1.0-unknown
Input Size 722436 != Roundtrip Size 0
52ea3834807742744a7cb6d040592c4f != 8cadf6b0feffffffb8733a00df343200
ROUNDTRIP_FAILURE

D:\Comics>lepton20160715.exe oots1039.jpg

**Shelwien** · 15th July 2016, 11:18

That's probably why there's the zlib alternative. But its a packjpg version anyway.
Also did you try -allowprogressive ?

**SvenBent** · 15th July 2016, 22:03

Originally Posted by Shelwien

That's probably why there's the zlib alternative. But its a packjpg version anyway.
Also did you try -allowprogressive ?

Nope the jpeg was not progressive but i might try tonight.
i was just unsure if the command line i did was correct or not

**load** · 16th July 2016, 16:43

so what does this do better than packjpg/packarc?

it does not compress better in my quick test, it might be faster, i can't test this right now.

it is hard to test it seems, with bigger files i get

lepton v1.0-unknown
Input Size 60934961 != Roundtrip Size 0
ceef1e51a728fcf9cf6cf97d95ffff33 != f9c3e628feffffffb873e000df34d800
ROUNDTRIP_FAILURE

and due to the fact it cannot handle wildcards, only small files can be tested. not very reliable.

/edit: ok, it IS faster, packjpg only uses 1 core.

too bad this here can't be compiled using mingw/gcc

**SvenBent** · 18th July 2016, 17:10

#8
Thats the same error i got. so ts an jpeg input size issue ?

**zubzer0** · 19th July 2016, 22:28

Original: 2000x3000 (6.00 MPixels) 19602KB [PNG-lossless]

Save as - JPEG, progressive, quality 60, subsampling 2x2(4:2:0) - 488KB
Lepton - 388KB (compress 20.5%)
WebP - 386KB (cwebp 0.5.1)
Jpeg2000 - 382KB (OpenJPEG 2.1.1)
BPG - 398KB (0.9.6, x265)

With forced subsampling 2x2 (4:2:0) in all formats.

Original: http://i023.radikal.ru/1607/6f/f2778e49dea4.png
Jpeg+Lepton http://s002.radikal.ru/i198/1607/7d/5607596e5734.png
WebP http://s013.radikal.ru/i324/1607/7f/d0e72e4269d9.png
Jpeg2000 http://s008.radikal.ru/i303/1607/3e/b1c969879ae4.png
BPG http://s017.radikal.ru/i427/1607/23/178a23eb312d.png

Full-Size: https://cloud.mail.ru/public/KxdX/6wSPKH9HW

**Jyrki Alakuijala** · 20th July 2016, 01:19

Originally Posted by zubzer0

Original: 2000x3000 (6.00 MPixels) 19602KB [PNG-lossless]

At quality 85 WebP [683 kB] removes freckles (blurring), at quality 75 jpeg [691 kB] adds more freckles (ringing, block boundaries). Cloth looks better on the WebP, but skin and hair looks better on Jpeg.

**Stephan Busch** · 27th July 2016, 11:35

Lepton is based on UncmpJPG sources of Matthias Stirner. It does work like packJPG but doesn't use its sources.

Can someone please create a batch file for windows so that multiple files or whole folders can be processed with Lepton?

In my intial tests Lepton is 3x faster than packJPG: the slow-best-ratio variant is about 2x faster.
Compression is sometimes better than packJPG, sometimes worse. To run executables in commandline I had to use
-skipverify switch to make it run with timer. It also compresses large JPEG - therefore I used -memory=1600M switch.
On some JPEG it crashes without warning, but the authors are kind and they are working on it.
I have also asked the author if wildcard support could be added but he told he needs help to make that happen,
so I created an issue in GitHub.

**Mauro Vezzosi** · 28th July 2016, 18:52

Originally Posted by Stephan Busch

Can someone please create a batch file for windows so that multiple files or whole folders can be processed with Lepton?

I don't know how to use Lepton (just see some examples), however I think that it could be enough something like this.

Line to be copied in a batch file (in this simple way you can pass up to 9 wildcards):
@for %%i in (%1 %2 %3 %4 %5 %6 %7 %8 %9) do @lepton "%%~i" "%%~i.lep"

Call the batch (e.g. WildLep.bat):
WildLep [Folder_To_Read\]Wildcard [...]

Folder_To_Read: optional (default: current folder), it is the folder where are the files.
Wildcard: obligatory, it can be a file name (e.g. file1), a file name with wildcard (file*), a list of the previous ones (file1 "file with space in the folder or name" a* b??? c\d*.e f\*)

Some examples:
WildLep *
WildLep "\test folder\file*" another_folder\only_one_file

You can execute this "for" also in the command line, replacing %% with %:
for %i in (*) do lepton "%~i" "%~i.lep"
for %i in ("\test folder\file*" another_folder\only_one_file) do lepton "%~i" "%~i.lep"

**SvenBent** · 29th July 2016, 04:07

for /D %i in (*.jpg) do Lepton.exe <commands> %i

let it rip

**Mauro Vezzosi** · 29th July 2016, 10:29

Originally Posted by SvenBent

for /D %i in (*.jpg) do Lepton.exe <commands> %i

let it rip

- /D uses *.jpg as folder name, not file name, perhaps did you mean to write /R (recurse into subfolders)?
- %i works in command line, in batch file (as requested by Stephan) you must write %%i.
- I think that %i (and %%i) doesn't handles file names with space in the right way, e.g. for file names "test_file_1.jpg" and "test file 2.jpg":

Code:

%i    -> Lepton.exe <commands>  test_file_1.jpg  <--  test_file_1.jpg   is 1 parameter 
"%~i" -> Lepton.exe <commands> "test_file_1.jpg" <-- "test_file_1.jpg"  is 1 parameter
%i    -> Lepton.exe <commands>  test file 2.jpg  <--  test file 2.jpg  are 3 parameters
"%~i" -> Lepton.exe <commands> "test file 2.jpg" <-- "test file 2.jpg"  is 1 parameter

**msat59** · 3rd August 2016, 14:14

The commandline parsing has a problem.

Code:

lepton a.jpg a.tmp
lepton v1.0-08c52d9280df3d409d9246df7ff166dd94628730
Failed To start subprocess with command line OS_ERROR

It must be lepton.exe. Please fix this bug, otherwise it cannot be used by FreeArc !

**Stephan Busch** · 3rd August 2016, 14:47

I am using this bat - not for drag & drop, but for commandline:

echo off
@for %%i in (%1 %2 %3 %4 %5 %6 %7 %8 %9) do @lepton-slow-best-ratio -skipverify "%%~i" "%%~i.lep"

pause

then I am using this commandline:

lepton.bat *.jpg

**SvenBent** · 3rd August 2016, 17:29

No need to put @ in front of the for line when you already have echo off, but you could but @ in front of the echo off command to hide it as well.
If you are only doing on line in you batch if would just remove the echo off and keep the @ before the for line to keep the bat as small as possible.

**Gonzalo** · 31st August 2016, 07:36

Hi folks! Quick thoughts:

1) I got an error on Windows 7 32 bits, using both the binary provided above and a build of my own of the last sources:

Code:

Failed To start subprocess with command line OS_ERROR

Any ideas?
2) On 'optimized' images (i.e. ECT) lepton performs actually better than PackJpg (compresses more densely)... Maybe later I can run again the tests so we can see the actual numbers.
3) Lepton is not case sensitive. On Linux this is an issue.
"lepton IMAGE.JPG" produces IMAGE.lep
"lepton IMAGE.lep" produces IMAGE.jpg
4) Can anybody help me doing parallel batches for linux? Like using ppx2 on Windows... Thank you in advance! This would be useful to compare PackJpg vs Lepton speed using all CPU resources.

**zubzer0** · 14th February 2017, 17:36

Hello,
Please help in assembling last commit, that was support processors below SSE4
https://github.com/dropbox/lepton

**Shelwien** · 14th February 2017, 22:00

It builds really easily from the list of *.c* files: http://nishi.dreamhosters.com/u/lepton20170214.exe
If that's what you meant.

**zubzer0** · 14th February 2017, 23:38

Shelwien
Thanks! On SSE3 (Core2Quad Q6600) works!
This very fast compression jpeg, and not bad results

**Stephan Busch** · 16th March 2017, 18:19

Would someone please post a win64 compile of latest Lepton?

**Jyrki Alakuijala** · 16th March 2017, 19:09

Would a JPEG recompression system that is 2.5x faster in (de)compression but 2 % worse density be more or less interesting than Lepton?

**Stephan Busch** · 16th March 2017, 19:17

I guess it would be interesting as well.

**dado023** · 17th March 2017, 00:53

Originally Posted by Jyrki Alakuijala

Would a JPEG recompression system that is 2.5x faster in (de)compression but 2 % worse density be more or less interesting than Lepton?

Honestly, since i mostly use images for storage or serving from web pages, i would prefer maximum possible compatible compression, no matter how long it takes in time or computing power......but decompression is another story, needs to be fast.

**dado023** · 17th March 2017, 01:16

Did anyone try to compare gueztli and lepton?

**Jyrki Alakuijala** · 17th March 2017, 01:50

Originally Posted by dado023

Did anyone try to compare gueztli and lepton?

Guetzli and lepton are complementary, i.e., it is possible to compare: libjpeg vs. guetzli vs. libjpeg+lepton vs. guetzli+lepton.

Guetzli should generate slightly less homogeneous entropy models, so further compression is likely going to be slightly less effective. I never actually tried lepton, but from a statistical viewpoint I'd assume you would get 14-17 % recompression for guetzlified images and the usual 22 % for libjpeg images.

**dado023** · 17th March 2017, 03:24

Originally Posted by Jyrki Alakuijala

Guetzli and lepton are complementary, i.e., it is possible to compare: libjpeg vs. guetzli vs. libjpeg+lepton vs. guetzli+lepton.

Guetzli should generate slightly less homogeneous entropy models, so further compression is likely going to be slightly less effective. I never actually tried lepton, but from a statistical viewpoint I'd assume you would get 14-17 % recompression for guetzlified images and the usual 22 % for libjpeg images.

Ok, so i am a bit confused....so, lepton is JPG compatible, correct?

How does jpeg-archive come into all this? cant it be combined for even smaller file sizes?

**pothos2** · 17th March 2017, 16:45

It is not compatible, lepton is a container format for JPEG files

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