Breakthrough In JPEG Compression 648
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."
Fractal image format (Score:5, Interesting)
Quite a while ago (years!) I had a program which could compress images into a fractal image format. It was amazing - the files were much smaller than JPEGs but looked a lot better. The only drawback was that it took ages to compress the images. But with the extra CPU horsepower we have today I'm surprised fractal image compression hasn't become more prevailant. It would still probably be useless for digital cameras though as it would probably be impossible to implement the compression in hardware/firmware such that it could compress a 6+ megapixel image within the requisit 1-2 seconds.
Does anyone know what happened to fractal image format files (.fif) and why they never took off?
Re:Fractal image format (Score:2, Insightful)
Re:Fractal image format (Score:4, Informative)
If the image compression algorithm was more efficient then there would be less data to write to the card and perhaps overall, it would actually be faster - even though the image compression algorithm might be slower.
Re:Fractal image format (Score:3, Informative)
Me: The main cause of delay is writing out the images to the memory card rather than compressing the images.
You: What takes time, is writing to the memory card, not compressing the JPEG's.
etc etc....
Re:Fractal image format (Score:3, Informative)
If the camera had to store the images in a small frame buffer designed for compressed images, then you wouldn't be able to save RAW images (or maybe only one - but that would make for a useless camera as they are 16mb + big and would take aaages to write out). So to me it was fairly
Re:True professionals don't use JPEG??? (Score:3, Informative)
Since the context was photography I should have said "true professional photographers
don't use jpeg to shoot their photos"After you have corrected the exposure, corrected the white balance, etc... and you are ready to throw away 12 bits per pixel of information... yes... jpeg may become useful.
The fact that many people doesn't care about 12 bits per pixel of information, about postprocessing degradation and so on, doesn't imply that it is good.
Re:Fractal image format (Score:3, Interesting)
Optimized hardware, specifically designed to run
I'd love to see something like this in a camera.
No doubt future Mars rovers would benefit from smaller download sizes?
Re:Fractal image format (Score:5, Informative)
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.
Re:Fractal image format (Score:3, Informative)
> which compresses anything amazingly well without strong evidence.
It's hardly mysterious. You can download trial versions and try it yourself - it's a well known compression technique that there are whole books about [amazon.co.uk]
There is near infinite evidence that it works so I don't know why you're doubting it. The issue isn't whether or not it works, it's why hasn't somebody made an opensource algorithm that we can all use.
The problem is that the exi
Re:Fractal image format (Score:5, Insightful)
Fractal image compression is generally useless for high-quality output. It's useful for low-bitrate applications. You can read about this in the Mark Nelson book.
The main reason fractal image compression was not picked up is the same reason algorithms such as IDEA are not very popular --- software patents. IIRC The company which holds the patents for fractal image compression made it clear that it was ready to defend its IP back in the 90s.
You can read about software patents too in the Mark Nelson book (the ones which apply to data compression).
Even the IJG JPEG software (not the standard) which we use today so commonly avoids arithmetic coding and uses baseline huffman compression for compressing the quantized output.
Re:Fractal image format (Score:4, Interesting)
Its not on their homepage anymore. I dont know if they really used IFS or they just did some wavelets and faked it, but the compression was honestly much better than jpeg. (but of course slower, too. IIRC, compressing a 1024x786 picture took about 40-50 seconds on my pentium.
What was unique was the viewer. it was "resolutionless", so you could zoom in farther than the original without pixelation. Shapes started to look painterly then, as if traced by outlines, which would actually be in favour of it really being a fractal compressor.
No idea why it was canned.
Re:Fractal image format (Score:2)
Re:Fractal image format (Score:3, Informative)
A program called Real Fractals has been in use by people who make very large blowups of images for years. It's pretty much standard practice to conver to Real Fractals before making a very big enlargement (like more than a few feet on a side).
Re:Fractal image format (Score:4, Informative)
Re:Fractal image format (Score:3, Informative)
I noticed the chart at the bottom of the whitepaper showed their "25-30%" figure was based on tests done on PNGs converted to JPGs at 50% quality. There is a lot of data degredation at 50% and I don't think many people regularly use anything below about 70%. I'd be much more interested in seeing what compression would be on a JPG straight out of a Digital Rebel or other camera set to
Re:Fractal image format (Score:2, Informative)
Re:Fractal image format (Score:4, Informative)
Re:Fractal image format (Score:5, Insightful)
I concluded that it isnt practical for general use, it took too much time to compress an image (alright it was five years ago and so today it probably wouldnt matter), but most importantly there is no easy general compression solution for all images (for instance one that compresses tree pics well wont do faces well and vice versa).
For a general dip into fractal image compression try to get and read 'Fractal Image Compression By Yuval Fisher'. Damn good read.
Re:Fractal image format (Score:4, Interesting)
I did some basic expirementation with Genetic Algorithms and fractal compression and I can tell you, GA does solve the problem. Not only solve it, but obliterates it. With GA, fractal compression can achieve compression ratios and quality that are unheard of with other techniques.
Of course, this is to be expected, after all - it is what nature does with us. Our genecode is the compressed image, our bodies are the uncompressed results.
Interesting thought food, huh...
Re:Fractal image format (Score:3, Interesting)
Its the deciding on what groups of pixels to store thats the problem, and that took an hour per machine on a 300MHz pentium 2.
A rough fractal compression algorithm is this:
1. Divide the pic up into subsets of itself, or pixel blocks. Simply Half it, quarter it, eighth it etc, down to 2x2 pixels. Th
Patents. (Score:5, Interesting)
Fractal compression is cool.. but encumbered by IP issues. Too bad.
Re:Fractal image format (Score:3, Informative)
http://www.jpeg.org/jpeg2000/ [jpeg.org]
I really don't understand why the camera etc companies doesn't adopt it.
they don't adopt it because.... (Score:3, Informative)
Re:Fractal image format (Score:3, Interesting)
Hard to implement. Patent mess. CPU requirements. No better fidelity [they have just as many artifacts as JPEG, but the artifacts are 'nicer looking']. Massive increases in available bandwidth. Fractal wierdness with editing, you always have to convert back to raster anyway.
The tech has found niche applications though, such as image scaling : Lizardtech's Genuine Fractals [lizardtech.com] is pitched as an image rescaling
Some link on Freactal compression (Score:5, Informative)
http://en.wikipedia.org/wiki/Fractal_compression [wikipedia.org]
Some sourceforge projects
http://sourceforge.net/projects/mpdslow/ [sourceforge.net]
http://sourceforge.net/projects/fractcompr/ [sourceforge.net]
for audio
http://sourceforge.net/projects/fraucomp/ [sourceforge.net]
Re:Fractal image format (Score:3, Interesting)
Why must we have it in 1-2 seconds? You could implement this a couple of ways without impacting the need for quick back to back shots. 1.) A compression button (menu option, or some such), allowing the owner to do a manual compress when running low on space. 2.) Do it automatica
Re:Fractal image format (Score:2)
You mean like GIF and MPEG and MP3 and probably this new scheme?
Re:Fractal image format (Score:2, Interesting)
You mean like GIF and MPEG and MP3 and probably this new scheme?
I should have elaborated. I remember when this was first written about. It was pretty amazing, but the inventors were charging for the right to implement a decoder, and (at least in the beginning) would not even let others to encode at all; the business model was apparently that you'd send them the images and they'd encode it for you.
Re:Fractal image format (Score:3, Informative)
Re:Fractal image format (Score:3, Interesting)
Fractal image compression was initially closely held, agressively marketed to developers (including us) for considerable bucks, and failed to make inroads in that venue. Now we'll have to wait for the patents to expire to consider it again -- it's been around for years and has gone literally nowhere, so I think the grandparent post h
Re:Fractal image format (Score:4, Insightful)
Patents do not tempt me. First, a good (solid) patent is expensive, both in terms of time and money. SOlid can be an illusion, too. Either here or on Kuro5hin, I saw a tag line in someone's message that mentioned a patent they hoped to make some money from. Or maybe I saw it on the web site. Anyway, what it appeared to be on a quick look was a method for selecting a bunch of different types of compression for an image format based upon an analysis of compressability for the local cell. If that's what it was, then we did it way back in 1985, called it PMBC and used it commercially for years. It was really fun, we presented graphs during the analysis of the image and you could see what modes were most common. Filters that eventually ended up in PNG were in there, too. See what I mean? So much for solid ideas. If no one says anything, or doesn't file for a patent at all, how do you know you're not just wasting your time and money? Of course, you don't.
Second, a patent completely exposes what you're doing (in sharp contrast to trade secret.) If you're laboring under the idea that only big companies that are easily found and attacked in court are the source of "they copied my idea!" problems, you're sadly mistaken.
Third, if someone infringes, it is very expensive to prosecute them, and if they don't have bucks themselves, there is nothing to be gained from it other than shutting them down, which isn't worth spit more often than not.
Patents, some people claim, allow you to sell an idea. That's fine, as far as it goes. If that's what you want to do. However, I simply observe that if you do not have a patent, what's to stop you from selling your idea then? You can still show it to people, sell it if you can convince them they want it, etc. For that matter, you can make them buy a patent, if they're so minded. Now -- if your idea is so freaking simple that once you show the results of it to someone, then they know what to do, then I humbly submit it wasn't worth patenting anyway -- my opinion (which isn't in line with how patents work by any means) is that trivial things are, and should remain, trivial.
But that's just me. :)
Re:Fractal image format (Score:5, Funny)
The results can be seen by the /. logo I have reduced here:
Re:Fractal image format (Score:4, Insightful)
Re:Fractal image format (Score:3, Funny)
Uh, dude - they just came out with this! So how can you say that? I would say this will actually ignite the minds of open-source compression experts (no, not literally) to rethink their approach to compressing JPEG, since they now know it's doable loselessly.
Re:Fractal image format (Score:2)
If you make something 100% bigger then it's twice the size. Somehow I thought that if you made the same file it 100% smaller again it'll be half the size
Re:Fractal image format (Score:5, Funny)
Re:Fractal image format (Score:5, Informative)
The heart of JPG is the DCT transform, performed on an 8x8 block basis. This is not being changed, since they claim that the original JPG can be reconstructed bit-for-bit exact. Hence their algorithm must be "lossless." Othewise, if you apply lossy compression to lossy compression, you get even more loss.
Here is the JPEG algorithm in a nutshell...
1) Convert RGB into Brightness, Color, and Saturation (three separate monochrome images).
2) Down-sample the Color and Saturation images. (This reduces the image size by 1/2; VERY lossy but you don't notice it)
3) Break each image into 8x8 blocks.
4) Perform a 2D DCT (discrete cosine transform) on each 8x8 block separately.
5) Quantize the DCT data using the special JPEG quantizaion matrix (this is where most of the loss happens)
6) Convert each 8x8 block of DCT data into a 64-number stream using the zig-zag scan (this just shuffles the order of the data, nothing more).
7) Apply a specialiazed huffman code to compress the data (lossless compression).
8) Write the header information, and dump encoded data to the file
I could be waaaay off-base on this, but I suspect that they have found a better replacement for the zig-zag scan and huffman coding steps. Optimizing another step would still be lossy, and could not re-create the original JPEG byte-for-byte.
But I must admit that I am completely baffled how they could take a huffman code optimized for JPEG and find something 30% better. Such a thing seems to be impossible, given what I know of coding theory (which, I admit, is a but rusty).
Re:Fractal image format (Score:4, Informative)
This page [datacompression.info] has a lot of information on arithmetic coding. Very briefly, it's a way of using fractional bits to encode symbols - Huffman coding encodes each symbol to some integral number of bits (more bits for infrequent symbols, fewer bits for common symbols); arithmetic coding does the same, but each symbol can map to a non-integral number of bits; you save a fraction of a bit per symbol, which can really add up. It's not easy at first to see how this works, but the math works out.
Arithmetic coding has another advantage over Huffman coding: with Huffman coding, you first collect symbol frequency information, then you build your coding table based on that frequency information. You then have to somehow encode the coding table in your bitstream (so the decoder knows how to decode the symbols). The coding table is based on an average over (often) the whole file, so it can't adapt to changes in the symbol frequencies: if one part of the file contains just numbers, and the other part contains just letters, their statistics get mixed together so you end up with a Huffman coding table that's not optimal for either part. Adaptive Huffman coding (changing the codewords as you encode the file, based on changing statistics) is possible but painful. On the other hand, adaptive arithmetic coding is very very easy.
LizardTech bought the fractal technology and (Score:4, Informative)
They have another imaging technology that they purchased from AT&T called DjVu. They've Open Sourced the viewer for that technology under the GPL [lizardtech.com].
I believe an encoder/decoder is also available [djvuzone.org] under a GPL license, though LizardTech doesn't appear to be happy with the GPL because they are pro software patents, and the GPL is not. The encoder/decoder may or may not be a fractal engine, someone more knowledgeable will have to answer that question.
LizardTech may be involved in a squable [ermapper.com] over the JPEG2000 technology. Something to do with patent litigation.
= 9J =
What's the point? (Score:5, Interesting)
I mean, it's cool and all to be able to compress JPGs by that much more, but the size gains are negated by the time it takes to decompress them. This seems just like those super high compression algorithms that have rather amazing compression rates, but take -forever- to compress or decompress, making them unusable. The difference is those are obviously and labeled as simply for scientific research into compression, but Aladdin seems to be trying to market this product for public consumption. The listed uses ( http://www.stuffit.com/imagecompression/ [stuffit.com] ) seem trivial at best.
Who's gonna be buying this?
-Cliff Spradlin
Re:What's the point? (Score:2)
Re:What's the point? (Score:2, Insightful)
Re:What's the point? (Score:2)
The 2 minutes time saving...remember it takes 6-8 seconds to compress as well, so multiply that by several thousand images. I don't k
Re:What's the point? (Score:2)
Bandwidth is the point (Score:5, Insightful)
Any websites with the primary purpose of hosting images would benefit greatly from this - such as art & photography sites. (Yes, and porn sites, too.)
Why? Because 99% of the traffic they generate is for their images. Of those images, 99% of them are in JPEG format. So this compression would give a good savings in bandwidth on all those pictures.
At large sites, a 30% cut in required bandwidth could mean a very large savings. Now, if they can take a large cut off their operating expenses, and all they need to do that is to make the users wait a few extra seconds for their pictures, I think we know what they'll do.
As for the decompression time, one thing to remember is that with how slow internet connections are (even broadband), you're much more likely to be waiting for one of these images to transfer than you are to be waiting for it to decompress (so long as it allows you to start the decompression without waiting for the end of the file, of course).
--The Rizz
"Man will never be free until the last king is strangled with the entrails of the last priest." -Denis Diderot
Re:Bandwidth is the point (Score:2)
(oppossed to this "patend pending" superalgorithm)
Btw: the "whitepaper" should be called "advertisement", because it contained zero technical information.
Re:What's the point? (Score:5, Funny)
You're right. I read the list, reproduced below. Who'd want to:
After all, electronic storage media is infinite, and bandwidth is free!Re:What's the point? (Score:2)
I can't really tell if you're being sarcastic here=)
Media IS cheap, as is bandwidth (provided you live in an area that provides it of course, but such areas are rapidly expanding). The price you pay for their product is probably a lot more than you get for not using some extra CD-Rs or DVD-Rs (which have incredibly small per gigabyte costs).
Benefits far outweighed by costs. (Score:5, Insightful)
Maybe if computers were a lot faster and the compression worked on any array of pixels, not just those that have undergone the lossy transformation of JPEG compression. But even then, it would have to do better than what PNG can do in terms of all the other things PNG does and no patented format will beat PNG at its game.
In theory what you say sounds nice, but in practice I genuinely can't recall a situation where a little more compression would have allowed me to send all the photos I wanted to via e-mail. But the reasons I mentioned at the top of this post are more important reasons why this should be rejected out of hand.
What meager benefits this affords are far outweighed by the costs. I don't see this going anywhere, and for very good reason.
Re:What's the point? (Score:2)
Roughly 25%, but who's counting? (Score:4)
Even in cameras where storage is tight, the bounds of memory is expanding all the time. Whereas a couple years ago the average storage card size was a measly 64Mb, today we are talking about gigabytes of storage memory inside our *cameras*!
So let's say we can squeeze another 30% of pictures onto a card. Does that really help us? Not really, if you consider that the compression itself rides atop JPEG compression and that computing time needs to be accounted for.
Currently, the fastest continuous shooting digital camera (the Nikon D2X) can only take 4 shots in a row before its memory buffers get full and the whole camera becomes useless. Compare that with the 9 shots per second F5 and you can see that the speed of shooting isn't going to cut it for digital cameras.
We need a compression method that is lossless, not one that creates compact files. Space is cheap, CPU cycles aren't.
Re:Roughly 25%, but who's counting? (Score:2)
Err, didn't you mean 'fast' rather than "lossless"?
Re:Roughly 25%, but who's counting? (Score:5, Informative)
I beg your pardon? Just about every digital SLR on the market is able to handle more than 4 images in buffer at a time. My year and a half old 10D can buffer 9 RAW images, and the D70 processes JPEGs before they hit the buffer, so it can buffer JPEGs in the dozens.
I doubt this is intended for any use other than archiving of images, where it will kick ass. It's clearly processor-intensive from the timing results, but for long-term storage that makes little difference.
I've got a few TB of images in storage and I'd love to be able to save 20-30% of that space, regardless of how cheap it is. That means a little longer between burning DVDs, and having more stuff on mounted drives for reference.
Re:Roughly 25%, but who's counting? (Score:5, Funny)
Re:Roughly 25%, but who's counting? (Score:3, Informative)
thats the fastest continuous shooting camera, you'll notice it has room for 40 JPEG frames in its buffer, and it shoots at 8.3 f/s
Questions (Score:5, Interesting)
1. Does this only work for JPEG, or also for other (compressed or plain) files?
2a. If it only works for JPEG, why?
2b. If it works for others, how well?
Anybody who can answer these?
Re:Questions (Score:5, Interesting)
In a nutshell, JPEG works like:
Original image data -> frequency domain -> high frequencies truncated (via division matrix) -> RLE
RLE is fast, but not terribly compact. Replacing it with something better improves compression. However, RLE generates not-very-compressable output, which is why traditional compression software does poorly. I imagine if you took a jpeg, undid the RLE, and zip compressed the result, you'd get something close to what the stuffit folk are claiming. If someone wants to try that, I'd be interested in the results.
Re:Questions (Score:5, Informative)
Re:Questions (Score:3, Interesting)
Thats the reason zip failes: its like zipping a zip. And try using rar on a zip compared to unzipping and raring the contends of the zip.
Re:Questions (Score:3, Informative)
JPEG doesn't just rely on RLE, but rather it is a Huffman-RLE combination. Basically, for each element in the DCT block, JPEG will code the coefficient value together with the number of 0-coefficient elements after this, with the code taken from a Huffman table.
Who would benefit fromt that? (Score:3, Insightful)
Gee, I wonder where you could license that format?
Man, they could have been a little bit more covert about their intentions and named it something a little less, umm, obvious.
The current formats might not be perfect, but at least they are (relativly) free.
Um (Score:2, Interesting)
We don't need any new standards unless the
Re:Um (Score:3, Insightful)
Moll.
Re:Um (Score:2)
Shhhh!...
They have a lot of CCDs and Memory cards to push out of stock yet.
Specialty Processors (Score:2)
Anyone know if the compression on a chip for the camera is a feasable idea, or am I just not awake yet.
DV Video? (Score:3, Interesting)
Didn't we just get rid of patented image files? (Score:5, Insightful)
However, do we want to subject ourselves to a new tax on images? If they make it, we don't have to go! Just say NO to patented file formats!
Re:Didn't we just get rid of patented image files? (Score:2)
If they start to enforce the patent immediately and are reasonable about it (going high volume instead of price), why not?
If however they intend to hide it in the closet and go "Ahaaaaah" ten years later, screw them.
Re:Didn't we just get rid of patented image files? (Score:3, Insightful)
since no one else has done additional jpg compression before,
You're kidding, right? [google.com] Don't buy into the patent office's self-serving assumption that software ideas are hard and deserving of government intervention. With 6,500,000,000 people in the world and the low entry bar for software it is a statistical certainty that most software ideas will be thought of by more than one person with no one person deserving protection.
---
Patents by definition restrict distribution and are incompatible with sta
Wow, that IS a breakthrough! (Score:5, Interesting)
WTF? (Score:3, Funny)
Re:WTF? (Score:2)
Bah (Score:2, Interesting)
But this is somewhat disappointing. The compression changes the format, and it must be decompressed to view it. Plus they don't intend on releasing the format, and their proposal for a new filetype which can be read by a "plugin" reeks of incomp
Patents? (Score:5, Insightful)
So, a question to slashdotters: do you think this kind of invention deserves to be protected by a patent? The standard response "software is already protected by copyright, patents are unnecessary" doesn't work, because anyone can study the code (even the binary will do), describe the algorithm to someone else, who can then reimplement it. Standard cleanroom process; takes only a couple of days for a competent team.
If you're RMS, you probably believe that no one has the right to own anything and all inventions and ideas belong to the public, but the majority of us will agree that that's a tad extreme. So whaddya'll think? Myself, I'm totally undecided.
Re:Patents? (Score:2)
Re:Patents? (Score:3, Insightful)
Re:Patents? (Score:5, Informative)
If you're RMS, you probably believe that no one has the right to own anything and all inventions and ideas belong to the public,
Nonsense, RMS has never [fsf.org] said that. Please read a more widely before making such malicious accusations again. Don't buy into M$ marketing smear and FUD campaign.
---
It's wrong that an intellectual property creator should not be rewarded for their work.
It's equally wrong that an IP creator should be rewarded too many times for the one piece of work, for exactly the same reasons.
Reform IP law and stop the M$/RIAA abuse.
It already exists :: DJVU (Score:2)
http://www.djvuzone.org/wid/
It's been around for a long time and open sourced.
Possibly just a rehuff? (Score:5, Interesting)
Ogg Vorbis stores its own huffman table in its own stream. The default encoder uses a table optimized for the general audio you can find out there. There is a utility called "rehuff" (goggle it yourself please) that will calculate and build a huffman table optimized for a particular stream and it seems that on average it reduces an Ogg Vorbis filesize by about 5-10%.
Building an optimized huffman table for individual JPEGs will probably yield such improved compression rates too. If the original JPEG tables are less optimized than the Ogg Vorbis ones, the reduction will be even higher. But 30% seems a little... optimistic.
Patent? (Score:2)
Looks slashdotted to me (Score:2)
Stuffit [nyud.net]
compress JPGs by roughly 30% [nyud.net]
whitepaper (PDF) [nyud.net]
And when will we learn about the patent? (Score:5, Insightful)
I've really seen enough of that (gif, mp3, jpeg) and i prefer spending the additional storage/bandwith capacity to another uppity "IP-shop" coming out to "0wn0rz" the internet with lawyering (maybe after a management-change).
Let's have another look at that compression algorithm in 20 years or so.
I did my final year project on Fractal Compression (Score:3, Interesting)
I wont bother going into the details of how it works (go read 'Fractal Image Compression' by Yuval Fisher*) but I concluded that fractal compression wasnt viable as there wasnt a general solution to suit all images. There are about 20 variables that you can decide, which give variable results to the final compressed image.
And one set of variables would be excellent to compressing pics of trees down 80%, another set of variables would be excellent compressing pics of animals down 80%, but using each others set would only give results equal or worse than normal compression algorithms.
Another factor at the time, five years ago, was that it took an hour to compress a 256x256 greyscale image on a 300MHz machine. Nowadays that isnt a factor.
* If anyone has this on ebook please post a link here, Im dying to read this again.
Re:I did my final year project on Fractal Compress (Score:2)
White Paper or Press Release? (Score:2, Interesting)
It describes a new format
Some might think it's a press release, since the "White Paper"'s discussion of the new format is largely limited to the benefits "OEMs" will have in using this (soon-to-be patented) technology, and explaining how it integrates into Allume's fine line of existence and future Digital Lifestyle(tm) products.
Some might further argue tha
open patents (Score:3, Informative)
JPEG - get it right (Score:3, Informative)
Here's why it works (Score:5, Informative)
The original JPEG compression algorithm had Huffmann coding for the DCT variables, but it also had some fixed-length codes for the beginning and end of blocks. If you set your compression at about 10x then you can hardly see the difference with real images. bring it up to 15x and the changes are still modest. However, yank it much over about 22x, and the image will go to hell. The reason is the block handling codes meant that a JPEG image with no data at all - a flat tint - would only compress at about 64x, so at 22x compression these block handling codes are about 1/3 of your overall code. The fractional bit wastage you get with using Huffmannn coding instead of arithmetic coding mops up some of the rest as you are usig shorter Huffmann codes. The codes are also very regular, as about 1/3 of the code is not particularly random. The 1/3 figure also matches the 30% compression figures too, which isn't surprising.
Why didn't the original JPEG developers make a better job of this? Well, doing an experimental DCT compression used to take me hours or days when I was developing on a shared PDP-11, and there was always the worry that a dropped bit would lose your place in the code, and scramble the rest of the image. A little regular overhead was also useful for things like progressive JPEG control. I guess we all knew it was not as tight as things could have been, but it got the job done. We knew if you want to get 40x compression, then reducing your image to half size, and the compressing that by x10 will look better. Unfortunately, people who just drag a slider to get more compression don't always know that.
The right solution would be to use JPEG2000 which has a much smaller block overhead, and so fails much more gracefully at higher compressions.
Somebody mod this up (Score:3, Interesting)
As another person who has implemented JPEG, I vouch for his accuracy :-)
just another humbug (Score:3, Interesting)
There had been, was, and has been possible to achieve better compression ratios, and guess what, even in the high times of JPEG we knew that what's inside, it's not the optimal solution. But there were certain aspects which made it stay the way it was, and that was good to be so. The same goes with JPEG-2000. Since the appearance of it there have been many attempts to make it better, and there have been some good results achieved (even I have read and sometimes even reviewed papers dealing with the subject).
It's really no question whether one can make an X% better compression to JPEG with the same quality (expecially today, when JPEG is so old that every joe and his dog had time to develop better ways). The question is, has it enough practical usability to justify its presence ? Is there a well-justified reason why we should use it ? Does it deliver
- better compression rates (smaller size with the same objective & subjective quality) ?
- lower compression times ?
- compatibility ?
- is it any better for hardware implementation purposes (same or lower computation times) ?
If it's just a "better" compression for the compression's own sake and not for our sakes, then this is even less news than me cleaning my room.
Super! (Score:4, Insightful)
After my experience there, can I expect to be led through a complicated and deceptive trick into downloading the trial version of some overpriced software, where I'm required to give up my email address, and the whole thing never works anyway? Stuffit might have great technology, but any company that wants to provide a proprietary format for anything will only be useful if *anyone* can open the format. Adobe knows that. And trying desperately to hook into people who *have* to turn to you to uncompress things and sell them things they most likely don't need isn't useful. It will just make StuffIt (.sit files) useless to people who *are* paying customers, because it's such a hassle for people to open the files.
Re:Only lossyless (Score:2)
Reading the comments about speed, I doubt this will be used for much besides archival - and there I'm thinking more about very large image files, or scanned documents where the size really can mount up - in other words, compressed TIFF images as you
Re:Only lossyless (Score:5, Interesting)
In other words, you did not understand what they did.
Re:Only lossyless (Score:3, Interesting)
PNG is lossless (Score:2, Interesting)
Re:Only lossyless (Score:5, Insightful)
You're misreading the whitepaper. What they're explaining here is different and actually quite clever.
Jpeg compression can be seen as consisting of two main steps. In the first, information in the image deemed unimportant is removed from the image. In the second, the remaining information is compressed losslessly.
It was already known that the second step is not the most efficient possible. Also, the jpeg standard supports both huffman and arithmetic-coding, however due to patent reasons I think arithmetic-coding (which is more efficient) is often not used. So what they're doing is just improving the efficiency of this second step. This works much better than attempting to encode the jpg binary itself, as anything performed following entropy coding will struggle to achieve much compression, as the data has been hugely complicated by the process and it is thus much harder to find any compressible patterns etc.
They've also improved the compression by a very impressive margin. Typically in the lossless compression world, gains are in the
Anyway, the end effect is the same regardless how the compression is achieved - they're taking a lossily-compressed jpg, and reducing its size. This obviously makes little sense to be say integrated into digital cameras, for which the jpeg2000 format is available anyway and features better gains and is much faster (yet is still awaiting mainstream adoption), however from the archival and theoretical-lossless-compression perspectives what they've allegedly achieved is pretty damn interesting.
Re:Only lossyless (Score:3, Informative)
the point about stuffit's improvement is that its so huge. sure
Re:Only lossyless (Score:3, Interesting)
It is this last step which is not particularly efficient. There are several reasons why ZIP cannot significantly compress this data. First, ZIP is a byte-oriented compressor. Huffman codes are bit-oriented. This causes ZIP to miss many patterns that could be backrefer
Re:The test includes bzip2, rar, zip etc... (Score:2, Informative)
Re:NEW FORMAT!!! (Score:2)
However they _are_ also planning a new image format, as well as considering applying the compression technology to mp3s and many other formats - virtually all these formats use similar entropy encoding methods which if we are to believe their claims they've improved on substrantially.
If they would apply their compression technology to improve say JPEG2000's wavelet compression by say 25% that would be well worth while. I'm sure theres a lot of people out ther