JPEGrescan is a perl script that uses jpeg tools to optimise jpeg compression by micro-managing some of the compression math based on research into some of the most common parameters.

NB: MozJPEG has the same optimisation built-in and is faster, so we recommend using MozJPEG when possible.

$ jpegrescan in.jpg out.jpg

• -s: Removes all Exif data and now all JFIF data as well. A basic 18-byte JFIF segment is added in its place.
• -i: Allows optimisations that may be "incompatible" with some software. Currently this means removing all JFIF data (saving 18 bytes) and allowing an encoding not supported by Opera before version 11.61.
• -t: Turns on multithreaded operation. Usually, uses up to 4 threads. Faster, but not four times faster than without -t. So try xargs -n1 -P to shrink a large number of jpegs at the same time.
• -a: Turns on arithmetic coding. Note this is unsupported by most software.
• -v: Verbose output.
• -q: Suppress all output.

JPEGrescan is known to be packaged in the following distributions:

• Arch's User Repository
• NixOS

• No out.jpg. Install the following:
  • Fedora: yum -y install perl-File-Slurp libjpeg-turbo-utils
  • Debian: aptitude install -y libfile-slurp-perl libjpeg-turbo-progs

First, thanks to Loren Merritt who created this script originally. Also, thanks to the people on devshed and lyncd - whose names seem to be lost to the sands of time - who came up with the jfifremove idea and the basic C code.