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Breakthrough In JPEG Compression
Kris_J writes "The makers of the (classic) compression package Stuffit have written a program that can compress JPGs by roughly 30%. This isn't the raw image to JPG compression, this is lossless compression applied to the JPG file. Typical compression rates for JPGs are 2% to -1%. If you read the whitepaper (PDF), they are even proposing a new image format; StuffIt Image Format (SIF). Now I just need someone to write a SIF compressor for my old Kodak DC260."
Maybe, but StuffIt is an archival program. If I have 10gb of existing jpgs and want to archive them, then this is whats wanted. Reencoding them as you suggest would be equivalent to converting say an mp3 to ogg format - a surefire way to lose quality with little gain.
Re fractal compression, people have been hyping it up for years but as far as I know it never really delivered. I'm dubious about any claims to some mysterious program which compresses anything amazingly well without strong evidence.
Wavelet compression however is used in jpeg2000 which is a bit better than jpeg but even that isn't supported by any digital cameras.
If StuffIt really does compress jpegs 25-30% that is a massive leap forward over the previous state-of-the-art compressors which reached I think around 3-4% - http://www.maximumcompression.com/data/jpg.php . Heres hoping their claims pan out, and that they release at least some details regarding the methods they used.
JPEG does not use Run-length encoding as its last compression step. Quote from the faq:"The JPEG spec defines two different "back end" modules for the final output of compressed data: either Huffman coding or arithmetic coding is allowed." http://www.faqs.org/faqs/jpeg-faq/part1/section-18 .html
It goes on to say that arithmetic coding is ~10% smaller, but is patented, so don't use it.
So what they are doing is removing the known chubby huffman coding and replacing it.