ainaleke / lepton

Lepton is a tool and file format for losslessly compressing JPEGs by an average of 22%.

Lepton

Lepton is a tool and file format for losslessly compressing JPEGs by an average of 22%.

This can be used to archive large photo collections, or to serve images live and save 22% bandwidth.

Build directions

Using a single core

./autogen.sh
./configure
make
make check

For multiprocessor machines:

./autogen.sh
./configure
make -j8
make check -j8

Using CMAKE:

mkdir -p build
cd build
cmake ..
make -j8

On Windows

mkdir -p build
cd build
"c:\Program Files\CMake\bin\cmake" ..
start .
REM Double click the Visual Studio project

Usage

To roundtrip (compress and decompress) an image, original.jpg, do the following:

./lepton original.jpg compressed.lep
./lepton compressed.lep restored_original.jpg

Or all at once:

./lepton original.jpg compressed.lep && ./lepton compressed.lep restored_original.jpg && diff restored_original.jpg original.jpg && echo no differences

Lepton may also be used with pipes -- be sure to check the exit code when using pipes as if compression fails lepton will produce 0 bytes and return a nonzero exit code (failure). In this case do not assume the 0 byte file is representative of the original.

./lepton - < original.jpg > compressed.lep
./lepton - < compressed.lep > restored_original.jpg

You may specify higher memory limits than the default for lepton to handle bigger images:

./lepton -memory=1024M -threadmemory=128M input_file output_file

Additionally you can configure lepton to process progressive jpegs. Warning: these take more memory to decode than normal JPEGs since the entire framebuffer must be kept in memory for the duration of the decompression, instead if just 2 rows of blocks.

./lepton -allowprogressive -memory=1024M -threadmemory=128M progressive.jpg compressedprogressive.lep

Submitting pull requests to lepton

Please begin by filling out the contributor form and asserting that The code I'm contributing is mine, and I have the right to license it. I'm granting you a license to distribute said code under the terms of this agreement.

at this page: https://opensource.dropbox.com/cla/

Then create a new pull request through the github interface