What does Lossless really mean?

Archived from groups: rec.photo.digital (More info?)

Freedom55 wrote:
> I have lossless rotation for digital photos in PSP8. Does lossless
> really mean lossless? I mean there has to be some loss in a jpeg when
> you rotate it.


There does not have to be any loss if your rotate by 90 or 180 degrees.

Scott

Archived from groups: rec.photo.digital (More info?)

Freedom55 wrote:

> I have lossless rotation for digital photos in PSP8. Does lossless
> really mean lossless? I mean there has to be some loss in a jpeg when
> you rotate it.


Yes, it's lossless.. Because the operation doesn't open
the file first, it doesn't have to re-compress it.. It's
the compression that causes the loss.

There's a good explanation on just about everything you
wanted to know about JPEG here:
``
http://makeashorterlink.com/?Z1BB6294B

Search the article for rotation and you'll find:


"There are a few specialized operations that can be done on a JPEG file
without decompressing it, and thus without incurring the generational loss
that you'd normally get from loading and re-saving the image in a regular
image editor. In particular it is possible to do 90-degree rotations and
flips losslessly, if the image dimensions are a multiple of the file's
block size (typically 16x16, 16x8, or 8x8 pixels for color JPEGs). This
fact used to be just an academic curiosity, but it has assumed practical
importance recently because many users of digital cameras would like to be
able to rotate their images from landscape to portrait format without
incurring loss --- and practically all digicams that produce JPEG files
produce images of the right dimensions for these operations to work. So
software that can do lossless JPEG transforms has started to pop up. But
you do need special software; rotating the image in a regular image editor
won't be lossless".

Archived from groups: rec.photo.digital (More info?)

jpeg isn't lossless, it's lossy, subject to the exceptions listed by the
others.

--
Regards
Ken.......................


"Dimitrios Tzortzakakis" <dimtzort@otenet.gr> wrote in message
news94ieg$e2f$1@usenet.otenet.gr...
> Lossless means identical to the uncompressed original.AFAIK jpeg is a
> lossless compression format, in contrast to MPEG which is lossy.That's why
I
> bought a digital still camera, but I stick to the good ol' 8 mm analogue
> camcorder format.
>
> --
> Tzortzakakis Dimitrios
> major in electrical engineering, freelance electrician
> FH von Iraklion-Kreta, freiberuflicher Elektriker
> dimtzort AT otenet DOT gr
> ? "Freedom55" <"joinertake this out"@ns.sympatico.ca> ?????? ??? ??????
> news:Y8ete.49313$Ph4.1315953@ursa-nb00s0.nbnet.nb.ca...
> > I have lossless rotation for digital photos in PSP8. Does lossless
> > really mean lossless? I mean there has to be some loss in a jpeg when
> > you rotate it.
> >
> > Ron
> > --
> > And it really doesn't matter if
> > I'm wrong I'm right
> > Where I belong I'm right
> > Where I belong.
> >
> > Lennon & McCartney
>
>

Archived from groups: rec.photo.digital (More info?)

David J Taylor
<david-taylor@blueyonder.co.not-this-bit.nor-this-part.uk.invalid>
wrote:

> Scott W wrote:
> > Freedom55 wrote:
> >> I have lossless rotation for digital photos in PSP8. Does lossless
> >> really mean lossless? I mean there has to be some loss in a jpeg when
> >> you rotate it.
> >
> > There does not have to be any loss if your rotate by 90 or 180
> > degrees.
>
> .. and the image is a multiple of 8 (or sometime 16) in each dimension.

Just to expand on that: You can lose data along the edges, and this is
likely to get clipped by rotation software, except under some
circumstances like the one above.

Archived from groups: rec.photo.digital (More info?)

Paul Mitchum wrote:

> Ralf Schmode <rschmode@gmx.net> wrote:
>
>> Dimitrios Tzortzakakis wrote:
>>
>> > Lossless means identical to the uncompressed original.AFAIK jpeg is a
>> > lossless compression format, in contrast to MPEG which is lossy.
>>
>> Hi, Dimitrios,
>>
>> sorry, that is not true. JPEG compression, as offered by consumer image
>> editing software on the market, is lossy even at 100% quality setting.
>
> This isn't strictly true any more. There's a newish format called
> JPEG2000 which has a lossless setting. Unfortunately, not much software
> supports JPEG2000 at the moment, especially the software in your camera.

Hi, Paul,

exactly that was I referring to when talking about "consumer software".
In other words: I don't see any contradiction between your words and
mine ;-)

Greets - Ralf

--
My animal photo page on the WWW: http://schmode.net (currently offline)
"Best of" portfolio: http://www2.fotocommunity.de/pc/pc.php4?mypics=254
My "adventure" of learning to ride: http://schmode.net/riding.htm
Mein "Abenteuer", Reiten zu lernen: http://schmode.net/reiten.htm

Archived from groups: rec.photo.digital (More info?)

On Sun, 19 Jun 2005 13:34:31 -0700, usenet@mile23.c0m (Paul Mitchum)
wrote:

->Ralf Schmode <rschmode@gmx.net> wrote:
->
->> Dimitrios Tzortzakakis wrote:
->>
->> > Lossless means identical to the uncompressed original.AFAIK jpeg
is a
->> > lossless compression format, in contrast to MPEG which is lossy.
->>
->> Hi, Dimitrios,
->>
->> sorry, that is not true. JPEG compression, as offered by consumer
image
->> editing software on the market, is lossy even at 100% quality
setting.
->
->This isn't strictly true any more. There's a newish format called
->JPEG2000 which has a lossless setting. Unfortunately, not much
software
->supports JPEG2000 at the moment, especially the software in your
camera.


Actually JPEG2000 isn't lossless either. But with the new compression
algorithms used it is much less lossy than JPEG or any other lossy
formats. It's advertised as lossless because it is visually lossless to
some pretty high level of compression. But if the developers are really
pushed on it they will admit that it is technically still a lossy
format. So for most general photographic purposes I guess it could be
said to be lossless. I suspect that there is still some number of
manipulations and resaves which would eventually render it visually
lossy as well.
MikeZ

Archived from groups: rec.photo.digital (More info?)

thx for all the answers, anyway, lossy or not, I like my digital camera very
much, while I think that it will be a long time when I 'll replace my 8mm
camcorder.

--
Tzortzakakis Dimitrios
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
Ï "David J Taylor"
<david-taylor@blueyonder.co.not-this-bit.nor-this-part.uk.invalid> Ýãñáøå
óôï ìÞíõìá news:KOtte.53131$G8.7495@text.news.blueyonder.co.uk...
> MikeZ wrote:
> []
> > Actually JPEG2000 isn't lossless either. But with the new compression
> > algorithms used it is much less lossy than JPEG or any other lossy
> > formats. It's advertised as lossless because it is visually lossless
> > to some pretty high level of compression. But if the developers are
> > really pushed on it they will admit that it is technically still a
> > lossy format. So for most general photographic purposes I guess it
> > could be said to be lossless. I suspect that there is still some
> > number of manipulations and resaves which would eventually render it
> > visually lossy as well.
> > MikeZ
>
> Both standard JPEG and JPEG 2000 do offer a truly lossless compression
> option with zero data loss, but this option is rarely implemented in
> consumer software, and (obviously) does not produce such small files.
>
> David
>
>

Archived from groups: rec.photo.digital (More info?)

"Freedom55" <"joinertake this out"@ns.sympatico.ca> wrote in message
news:Y8ete.49313$Ph4.1315953@ursa-nb00s0.nbnet.nb.ca...
> I have lossless rotation for digital photos in PSP8. Does lossless
> really mean lossless? I mean there has to be some loss in a jpeg when
> you rotate it.

Display a jpeg on your monitor, then pick up the monitor and physically
rotate it by 90 degrees. How much data have you lost by doing this?
Rotating a jpeg by 90 degrees is a rows-and-columns book-keeping issue which
does not require the existing data in the file to be re-compressed, only
rearranged. Some restrictions apply, as the travel ads say:

" Lossless Rotation: The rotation of an image without the loss of image
quality. This works best on images with dimensions that are a multiple of 8
or 16. ACDSee digital photo software includes a lossless rotation function.
"

--From the ACDSee glossary, obtained using the Google search expression '
define: "lossless rotation" '. Include the double quotes, but not the
singles.


But always remember that even data in a normal jpeg rotation are never truly
lost--they're just waiting for you in jpeg heaven. Or so it is written.