Impressive JPEG Recompression | Hacker News Reader

Impressive JPEG Recompression

jpegmini.com

122 pointsfranze61 comments

I once worked somewhere where we had a need to store and transmit lots of camera created jpegs in as efficient a manner as possible.

When working on this problem, I noticed that all digital cameras create jpeg with 422 sampling. This might be a religious topic for some, but I cannot see any visual difference between 4:2:2 and 4:2:0, even with high magnification or on physical prints as large as 30 inch height. Simply sub-sampling to 4:2:0 along with subtle tweaks to quantization tables and with little effort we'd bring a typical jpeg from 1-2MB down to 300-400KB.

We even did a series of experiments with people who look at photo prints all day and they could not reliably pick the 'recompressed' images.

The only reason I think people really hold on to 422 or even 444 is that when subsampling you can get nasty amplified errors if you are using two tools that sampling with different algorithms or from different siting (i.e. imaging if one tool picked odd lines and one picked even). Although the spec specifies siting, I think there are still people who do it wrong, not to mention there is still leeway for interpretation on how pixels are averaged for siting that is not on a pixel boundary.

Bottom line is that if you know exactly what you are going to do with the photo in the future you can compress a lot and quite easily with little risk. If you have a lot of unknown processing in the future, things can get dicey.

For those wondering about the differences between 4:2:2 and 4:2:0, check out http://en.wikipedia.org/wiki/Chroma_subsampling#4:2:0

4:4:4 sampling is necessary to preserve color distinction in screenshots (otherwise your icons and text may change color), but since very few photographs will have single-pixel color variation, 4:2:0 is usually sufficient. Don't get me started on 4:1:1, though... I'm glad to be rid of the chromatic curse that was miniDV.

I started with this image: http://c.ourdoings.net/td/kg/7cj8d5l.jpg

It shrunk it 1.5x. I downloaded the _mini version and could see more artifacts in the rendering of some of the smooth surfaces.

Then I re-uploaded the _mini version to jpegmini. It shrunk it 1.3x. This shows that they are reducing quality, not just optimizing.

Given that they claim to perform perceptual optimization, I would expect this. Human perception wouldn't come into play if they were just optimizing the image.

I've successfully converted 99% quality image which became 4.4 times smaller in size (identify shows 72% quality) after that I've converted same original image to 72% quality with imagemagick and I've got similar compression. Artifacts are look similar to jpegmini algorithm.

More interesting would be blind comparison experiment with with imagemagick compressed images with similar compression ratio. I'd be surprised if they could get 25-50% better compression with similar quality images.

"So far, 14 patent applications have been submitted for various technologies included in JPEGmini"

14 patents for one algorithm??? Somebody lost their mind, I worked on a camera lens that had 10 elements and less patents than that. Craziness.

I suspect those patents are designed to serve as a deterrent for anyone to enter the "JPEG optimization market".

Also, the service itself is underwhelming - it does next to nothing on JPEGs that are already optimized.

That will work. Even just the possibility of patents has served to keep people out of that market:

http://en.wikipedia.org/wiki/JPEG_2000#Legal_issues

A comment from reddit:

http://web_design.reddit.com/comments/jdo4v/_/c2balp2

> barfolomew 13 points 20 days ago

> In my experience, one should stay away from Israeli tech startups. They're often very aggressive and fly-by-night operations. The culture clash between a north american firm is hard to deal with.

Is this really the case?

Generally, no. But when one claims personal experience, how can a stranger judge?

By asking for more detail.

Fight generalization with generalization! When one encounters, "one should stay away from <race or ethnic group>", always proceed with caution.

While that is a reasonable policy, the statement in question is one of regional culture. Compare "silicon valley startups".

Some are, most aren't. There are scammers and hucksters everywhere. It is always easier to scam people when they don't really know you, a fact that can benefit foreign start-ups in the US market.

That said, regarding Israeli companies, I personally object to Israeli companies that operate from illegal Israeli settlements in the occupied Palestinian territories, such as SodaStream and Ahava Cosmetics. SodaStream is particularly bad in that it produces its goods using underpaid Palestinian labor but market's its products as made in Israel.

SodaStream details: http://www.whoprofits.org/articlefiles/WhoProfits-Production...

Please add a non-flash alternative uploader.

I run as little flash as possible these days, security, tracking etc.

Aha! Look what I discovered:

http://www.jpegmini.com/main/shrink_photo?no_flash=1

There have been a dozen jpeg reduction attempts over the years, curious to play with this one. Lossless jpeg cropping fascinates me more though.

Is such sorcery possible?

You can crop and rotate JPEGs losslessly:

http://jpegclub.org/jpegtran/

Doesn't cropping have to be within a certain size, though?

EDIT: Yep, looks like you can only crop it along the DCT block boundaries:

http://www.ben.com/jpeg/

Calvin Hass has several articles on JPEG, including lossless transformations. http://www.impulseadventure.com/photo/

Better JPEG sells a library, Photoshop plugin, and (relatively simple) standalone program that allow lossless editing (only changed blocks are recompressed). http://www.betterjpeg.com/

If you want recompression without quality loss, try jpgcrush: http://akuvian.org/src/jpgcrush.tar.gz

It does some quite evil things with progressive Huffman coding that most people didn't even realize was possible.

I'd be interested in seeing how this works (source, docs, etc.), but unfortunately I can neither get jpgcrush nor jpegrescan to output anything.

This introduces noticeable artifacting for me. jpegtran -- run via the wonderful imgopt (http://lyncd.com/2009/03/imgopt-lossless-optimize-png-jpeg/) script -- did a better job with the image I uploaded, with no quality loss.

If you're looking for something similar but in GUI form, I made http://trimage.org for that, installable in Ubuntu via apt-get install trimage.

Another site from Sharon Carmel (the author based on WHOIS info)

http://iloop.co.il/

He/She is BeInSync founder and VP R&D

http://iloop.co.il/main_page/2009/9/14/we-have-a-dream.html

http://www.israelinnovation20.com/tag/sharon-carmel/

Someone with that name posted to the WebP list about Jpegmini, they came across as a bit of a kook (though it could have been a language issue I suppose):

https://groups.google.com/a/webmproject.org/group/webp-discu...

Well the quality seems quite a bit worse for the picture I tried. Original: http://postimage.org/image/94ol50ck/, compressed: http://postimage.org/image/14712qgjo/ The resulting image has way less detail in higher frequencies.

Looks like the compressed version is a bit sharper to me.

If the compressed version is apparently sharper than the original file, that's an artifact surely? It might be pleasing in some contexts but it's not an accurate representation of the original file in that aspect.

I mean, vytis claimed that

> The resulting image has way less detail in higher frequencies.

But the compressed version actually exposes more detail.

But the compressed version actually exposes more detail.

No. It really doesn't.

It adds a couple of visual filters (brightening, sharpening) before recompressing, but these don't "expose more detail", but rather all three steps actually introduce additional errors. Errors that trick they eye into seeing a "better" image, but errors nonetheless.

JPEGmini does not apply any filters on the photo, no pre processing whatsoever. JPEGmini went through BT.500 certification, the result was that given 2 images 1. source 2. recompressed, the tester could not tell which is the source and which is the recompressed. Enjoy.

I'm not sure what BT.500 certification is, but I can certainly tell the difference on some (not all) images, when recomposed.

Are you attached to JPEGmini? If so, would you be willing to bet that I cannot tell if a photo of my choice has gone through your system and been compressed?

I'm on a 3G connection today, so relied on this thread for before/after images. Unfortunately, it seems that the original poster had labelled his photos the wrong way around...

Think he might have got the links the wrong way round

Sorry, I pasted the links in the wrong order. The original is this one: http://postimage.org/image/14712qgjo/ and the compressed image: http://postimage.org/image/94ol50ck/ File size was reduced from 4.4mb to 1.2mb

looking at the file names I think this is the compressed version http://s3.postimage.org/2qgfsekg7/Front_mini.jpg

I'd like to run it through errorlevelanalysis.com but their service seem to be down.

I suspect it tries to raise the brightness and sharpness of certain pixels before compressing it further so "important" elements stay in detail. What was done to your image though looks nothing like the quality of their examples for the ship, etc.

Custom quantization tables and chroma subsampling, with a bit of hype

Wow, the Dropbox sample photo Costa Rican Frog was reduced 4.6x and actually looks sharper than the original. The detail in the middle of the back appears to have more contrast in the minified version. Other than some sharpness and some minor artifacts in the eye, the before and after images look identical. Except the original is 346KB and the JPEGmini version is 75KB.

looks sharper than the original ... more contrast in the minified version

That's not a good thing, to my way of thinking. When I'm processing my photos, I'm choosing very carefully the amount of sharpness and especially contrast in the image. I'd be very unhappy with a tool that alters these.

It looks to be a per-image effect and not intentional. Most images I tried, there was no apparent difference. Then again, most images had only about a 30% savings. For an almost 80% savings, I'm not surprised if there's no free lunch.

It's impressive, indeed! I guess they use some feedback loop when recompressing, because there doesn't appear to be no quality loss, even on the smallest details. I've tried one file of 1.4MB of an Australian nature landscape. Recompressed went under 400KB. I wonder if there isn't an offline tool available. For free if possible :)

  > there doesn't appear to be no quality loss, even
  > on the smallest details

I do not think that means what you think it means.

inconceivable!

two relevant papers

http://spie.org/x648.html?product_id=872231

http://spie.org/x648.html?product_id=872230

from SPIE Electronic Imaging 2011 conference in San Francisco

Wow it looks like they've caught on to something. I've tried a few ~1.2 MB scans of film negatives and it shrunk the sizes 5x and 6x with no differences that I can see. When I tried smaller files however the difference got down to ~1.5x with some more obvious noise removal so I think it's just exploiting inefficiencies in how large jpg's are encoded.

I also love the sense of humor. "SEEMS YOUR PHOTO LOST SOME WEIGHT!"

I don't see the point. I upload a jpeg that is 51% progressive compressed in Photoshop and Jpegmini can reduce the size 1.2x.

Isn't really worth the effort.

This would be interesting if it was not web service. I would like to have an executable with command line access, in order to run batch commands. I don't want my images stored/processed on their server. Surely they can think of a license price.

A more web-ish example: a static jpg banner with 900x400 was 46KB and got compressed into 35KB (reduction of 1.3x). Another similiar banner with 43KB resulted in a compressed 29KB (1.5x smaller). This is very good!

Does what it says. Took a 1MB image and took it down to about 300kB. Only complaint is that you have to sign in (using Facebook/Google) or create an account to do batch uploads.

Every jpg image I try fails. This happening to anyone else?

No. I tried Windows7 Chrysanthemum.jpg under Sample Pictures folder, it works, impressively.

64 bit browser + flash on Windows = fail for uploads use a 32 bit browser (like IE..) and see if it fixes it also, blame adobe

Whoa! 1.15mb jpeg | 1.1mb imageoptim | 422 kb jpegmini

So far, 14 patent applications have been submitted for various technologies included in JPEGmini

Must be a good chunk of change behind it.

I wonder if one could figure out the algorithm by making a specially crafted image and recycling it through their service several times to see what it does where.

This is great, shaved ~20% off my splash image, 100kb to 80kb with no noticeable loss of quality.

Good job!

Ratio display needs to be fixed:

99k -> 71k is not usefully presented as 1.4x, but better as ~30%

Or 70% the size.

Tried it. It just saves it with worse compression, resulting in more artifacts. Not impressed.

All these posts "whoa I compressed my 1MB image to 400KB" are laughable. It's not like it's lossless.

You are very right, rorrr

Reply on news.ycombinator.com