On Jan 19, 1:38 pm, Ron Hunter wrote:
Sachin Garg wrote:
There are a number of tools available which can do "lossless"
compression of jpeg files, they get around 20-25% compression. There
are both commercial/proprietary (StufIt) and free/open-source options
(PackJPG, PAQ etc...).

Have you tried any such tool? Do you use any?

I am in process of publishing an image compression benchmark and want
to know what is in actual popular use and what all is only
academically interesting.

And if not, then why not? what do you think is missing in them that
would make you change your mind?

JPEG and 'losless' are really mutually exclusive terms.
The whole idea of JPEG compression is to achieve high compression rates
(6:1 or better), by discarding information not required for satisfactory
image quality, and then applying a standard compression technique, such
as LZW with Huffman, to the result. Leaving out the lossy step results
in dramatically reduced compression. Not worth bothering with.

You are correct that JPEG is lossy. These tools apply further lossless
compression on jpeg files.

Think of it as something similar to using zip.

Sachin Garg [India]
www.sachingarg.com | www.c10n.info