JPEG 2000 compression

[David Barkin]

Hi MarcV

I've never used JP2000 but I'm sure it's everything you say it is. However there are two points to take into consideration.

1. It's proprietory so that at least for now if you yourself saved an image and tried to give it to me, I couln't read it.

2. The latest release of Photoshop has a standard JPEG option which is lossless. It compresses files to about 25 percent of original, so still a very convenient storage format.

So J2000 will catch on only if it's more freely available.

I might speak differently if I was into video, where it probably has more uses but for photography it doesn;t make sense at the moment. Perhaps things will change...

Dave

A great free tool that lets you see the difference between ordinary
JPEG and JPEG2000 can be downloaded here:
http://www.aware.com/products/compression/j2k_download.html

 

[MarcV]

I've never used JP2000 but I'm sure it's everything you say it is.
However there are two points to take into consideration.

1. It's proprietory so that at least for now if you yourself saved
an image and tried to give it to me, I couln't read it.

I agree, there's unfortunately almost no software that supports the format. Still, the format itself is very promising. The program I'm pointing to lets you see the difference in image quality between regular JPG and J2K at equal compression ratios. It shows that J2K is far superior over JPG, even at very high compression ratios.

2. The latest release of Photoshop has a standard JPEG option which
is lossless. It compresses files to about 25 percent of original,
so still a very convenient storage format.

I would be glad if you could show me where to find it. I have PS7 but cand find that option...

 

[theswede #100093]

I agree, there's unfortunately almost no software that supports the
format. Still, the format itself is very promising.

Any wavelet based compression format has the same properties. There's no need to go for jp2 as it's locked in to make money; it's very likely that unless some big players open up jp2 and include it in defacto software (such as Windows or AOL), some other open wavelet format (such as GWIC) will take this throne.

Of course, this can happen in parallell.

The program I'm
pointing to lets you see the difference in image quality between
regular JPG and J2K at equal compression ratios. It shows that J2K
is far superior over JPG, even at very high compression ratios.

The program is designed to sell jp2. I wouldn't trust any comparisons it creates. Do they state what JPEG implementation they use? The difference can be astonishing.

Also, jp2 is not even superior at high compression, it's only superior at high compression. At lower compression ratios it's better at some pictures, worse at others. Not until you reach pretty extreme ratios does it make a difference.

I would be glad if you could show me where to find it. I have PS7
but cand find that option...

There is no option, and no JPEG is truly lossless, but highest quality JPEG in PS7 (and in Gimp as well) is so high quality that the difference is just about academic.

--
Jesper

 

[David Barkin]

Hi MarcV

1. It's proprietory so that at least for now if you yourself saved
an image and tried to give it to me, I couln't read it.

I agree, there's unfortunately almost no software that supports the
format. Still, the format itself is very promising. The program I'm
pointing to lets you see the difference in image quality between
regular JPG and J2K at equal compression ratios. It shows that J2K
is far superior over JPG, even at very high compression ratios.

I don't doubt that, and if it was a standard format no doubt I would be using it. However the truth is I don't like any lossy format, never shoot in JPEG and have only started to archive in JPEG with the advent of PS 7.

2. The latest release of Photoshop has a standard JPEG option which
is lossless. It compresses files to about 25 percent of original,
so still a very convenient storage format.

I would be glad if you could show me where to find it. I have PS7
but cand find that option...

Sorry, I used the wrong word. The "option" is simply selecting #12 in the save JPEG dialogue. In the last few weeks there have been a number of threads discussing this. I should add that I was a sceptic until I saved a number of images from 12 to 20 times and could find no difference even on a pixel level.

Dave

 

[David Barkin]

Hi TheSwede

I would be glad if you could show me where to find it. I have PS7
but cand find that option...

There is no option, and no JPEG is truly lossless, but highest
quality JPEG in PS7 (and in Gimp as well) is so high quality that
the difference is just about academic.

Can you tell me a way to see the loss? After saving and resaving I have not been able to find a single pixel that is different, even after 20 resaves. I welcome the opportunity to be proved wrong.

Dave

 

[theswede #100093]

Can you tell me a way to see the loss?

Just compare the stored information with the original information; lossy is a way to compress, it doesn't necessarily indicate that the decoded image is not identical to the original image.

After saving and resaving I
have not been able to find a single pixel that is different, even
after 20 resaves. I welcome the opportunity to be proved wrong.

There's nothing to prove; a good lossy algorithm works that way. Not all pixels are saved in the file, some are recreated when redisplaying the file. That's what lossy means.

Any good lossy compression will work this way. jp2 is better at high compression, but at low compression it's hard to get any better than current JPEG.

--
Jesper

 

[Frenchy]

this point. I'm not even sure if JPEG 2000 is "JPEG." Its certainly
not compatible. They probably picked that name because of the
format name recognition (I'll be happy to be corrected on this last
point).

the name is very close because the compression is also close. JPEG uses Fourrier transform on 16x16 squares in your picture. Lately, the maths have improved and the Fourrier transform has been refined into the wavelet transform .The JPEG2000 format is based on the same principle as the JPEG (frequency transformation of your image), but with a more complex math transform. The 2 are of course not compatible, but rely on the same idea.

Hope this helps.

Certainly for the moment you will have no one to give these files
to, simply because very few users use this format.

yes, few user and even fewer software can read/write it. I'm not even sure the format in completely defined. We are at the early steps of implementation.

Frenchy

 

[David Barkin]

Hi Frenchy

Much thanks for the informative post!

Dave

this point. I'm not even sure if JPEG 2000 is "JPEG." Its certainly
not compatible. They probably picked that name because of the
format name recognition (I'll be happy to be corrected on this last
point).

the name is very close because the compression is also close. JPEG
uses Fourrier transform on 16x16 squares in your picture. Lately,
the maths have improved and the Fourrier transform has been refined
into the wavelet transform .The JPEG2000 format is based on the
same principle as the JPEG (frequency transformation of your
image), but with a more complex math transform. The 2 are of course
not compatible, but rely on the same idea.

Hope this helps.

Certainly for the moment you will have no one to give these files
to, simply because very few users use this format.

yes, few user and even fewer software can read/write it. I'm not
even sure the format in completely defined. We are at the early
steps of implementation.

Frenchy

 

[David Barkin]

Hi The Swede

The reason I asked the question is because the common definition of lossy is that actual image data is lost. So with all due respect, can you give me a definite answer? I'm under the impression that no ACTUAL image data is lost. So, by the definition I'm using the #12 JPEG option of Photoshop is lossless. Just as compressed TIF is lossless. So if I'm wrong in either definition I'll be happy to be corrected. My statements are primarily based on what someone else posted on a related thread and my own testing - Not from reading any technical literature.

Dave

Can you tell me a way to see the loss?

Just compare the stored information with the original information;
lossy is a way to compress, it doesn't necessarily indicate that
the decoded image is not identical to the original image.

After saving and resaving I
have not been able to find a single pixel that is different, even
after 20 resaves. I welcome the opportunity to be proved wrong.

There's nothing to prove; a good lossy algorithm works that way.
Not all pixels are saved in the file, some are recreated when
redisplaying the file. That's what lossy means.

Any good lossy compression will work this way. jp2 is better at
high compression, but at low compression it's hard to get any
better than current JPEG.

--
Jesper

 

[theswede #100093]

The reason I asked the question is because the common definition of
lossy is that actual image data is lost.

No. The definition of lossy is that data is discarded and then reconstructed. In the ideal case (algorithm good for the data to be compressed) the reconstructed data is identical to the original. In the good case it's close enough that for the intended use it doesn't matter.

JPEG is very near the ideal case in photographs and low compression.

So with all due respect,
can you give me a definite answer? I'm under the impression that no
ACTUAL image data is lost.

No perceptible loss is likely to occur at low compression rates. Actual image data loss is inherent in the JPEG algorithm and always takes place.

So, by the definition I'm using the #12
JPEG option of Photoshop is lossless.

By definition, JPEG is lossy. No getting around it.

Just as compressed TIF is lossless.

No. TIFF uses lossless compression, as does GIF and PNG. JPEG uses lossy compression.

So if I'm wrong in either definition I'll be happy to be corrected.

Consider your terminology corrected. From a computer science standpoint it doesn't matter what the resulting image looks like; if the algorithm discards and then recreates data, the algorithm is lossy. Even if the recreation in some cases is identical to the original.

My statements are primarily based on what someone else
posted on a related thread and my own testing - Not from reading
any technical literature.

As I said before, a lossy compression algorithm only means that data is discarded in order to compress better. It doesn't mean that the image will inevitably degrade, or for that matter that any loss will be noticed. In fact, the algorithm is designed to minimize perceptible loss.

Using a suitably sophisticated analysis tool you'll be able to detect the changes, but if you can't tell the difference by examining the pictures even in detail, does it really matter?

--
Jesper

 

[Igor R.]

I'm not

even sure the format in completely defined. We are at the early
steps of implementation.

Thats the point! The standart is not completed yet. When they will complete it, its gonna be EVERYWHERE!

 

[Igor R.]

Can you direct me to the source code that I can use in my own GPL'd
programs then, please?
Even just source for a Linux plugin that works in Mozilla and Opera
would be a start, as long as it's not locked licensed.

You gotta buy Part 1 and 2 from ISO, those docs got all necesary info (with examples) about how to write JP2 compressor and decompressor.

That's why I see everyone rushing to adopt it, I take it?

It is not yet completed, but now at the final stages.

 

[Igor R.]

Any wavelet based compression format has the same properties.

Not really, they are little different.

There's no need to go for jp2 as it's locked in to make money; it's
very likely that unless some big players open up jp2 and include it
in defacto software (such as Windows or AOL),

AOL itself is nothing, it used Explorer DLL's to read images.
The most important parts are browsers and Photoshop (Quark, Pagemaker)!

some other open
wavelet format (such as GWIC) will take this throne.

Nobody knows about GWIC. I thing the most popular wl format for today is LuraWawe.lwf

 

[Igor R.]

Can you tell me a way to see the loss? After saving and resaving I
have not been able to find a single pixel that is different, even
after 20 resaves. I welcome the opportunity to be proved wrong.

Mathematical algorythms of ordinary JPEG doesn't imply loseless compression. Like you're unable to loselessly copy from one analog tape to another even if it is BetaCAM SP!

 

[Nils Haeck]

So, by the definition I'm using the #12
JPEG option of Photoshop is lossless.

By definition, JPEG is lossy. No getting around it.
--
Jesper

Well this is not completely true. In the JFIF spec there IS a lossless JPG mode. It is, however, almost never used or implemented in software. But perhaps the #12 JPEG option in Photoshop is this lossless variant.

The lossless JPG mode works by predicting the difference of part X of an image from the preceding surrounding blocks of this part, and only storing the difference (in a smart way). It is inherently lossless, does NOT contain the lossy DCT - discard - IDCT step.

--
Nils Haeck
Developer of ABC-View Manager (image management software)
http://www.abc-view.com

 

[theswede #100093]

You gotta buy Part 1 and 2 from ISO, those docs got all necesary
info (with examples) about how to write JP2 compressor and
decompressor.

That's not enough. I also have to pay per copy license fees.

JPEG2000 is a dead end.

That's why I see everyone rushing to adopt it, I take it?

It is not yet completed, but now at the final stages.

I hope it never, ever takes off. Proprietary formats are death to innovation and development.

--
Jesper

 

[theswede #100093]

I'm not

even sure the format in completely defined. We are at the early
steps of implementation.

Thats the point! The standart is not completed yet. When they will
complete it, its gonna be EVERYWHERE!

I so hope you're wrong. You don't know how much. JPEG2000 is an inherently flawed and locked in system.

Prove me wrong; give me a fully free implementation in GPL compatible format, and I'll gladly support it fully. Until then, I will treat it like I treat Microsoft Word files; as an evil that has to be eradicated.

--
Jesper

 

[MarcV]

I knew about this lossless JPG option, had read about that somewhere too. That's what I thought David Barkin was referring to in PhotoShop, but I'm not convinced it's actually there...

Well this is not completely true. In the JFIF spec there IS a
lossless JPG mode. It is, however, almost never used or implemented
in software. But perhaps the #12 JPEG option in Photoshop is this
lossless variant.

The lossless JPG mode works by predicting the difference of part X
of an image from the preceding surrounding blocks of this part, and
only storing the difference (in a smart way). It is inherently
lossless, does NOT contain the lossy DCT - discard - IDCT step.

 

[theswede #100093]

Well this is not completely true. In the JFIF spec there IS a
lossless JPG mode. It is, however, almost never used or implemented
in software. But perhaps the #12 JPEG option in Photoshop is this
lossless variant.

Wow ... can't trust any specs to be consistent these days. Sounds like JPEG is almost as messy as TIFF

No, I'm just kidding.

The lossless JPG mode works by predicting the difference of part X
of an image from the preceding surrounding blocks of this part, and
only storing the difference (in a smart way). It is inherently
lossless, does NOT contain the lossy DCT - discard - IDCT step.

Kind of a block variety of LZW? Or some smarter prediction?

Not that it matters, doesn't sound all that efficient, and for lossless I'd just go PNG anyway.

--
Jesper

 

[pazooter]

It seems to give a highly accurate indication as to what level a jpg has been compressed. And it's FREEWARE!

http://www.mediachance.com/digicam/jpgq.htm