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What does Lossless really mean?

 
 
Freedom55
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      06-19-2005
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
 
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Scott W
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      06-19-2005
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

 
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David J Taylor
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      06-19-2005
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.
>
> Scott


... and the image is a multiple of 8 (or sometime 16) in each dimension.

David


 
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Jim Townsend
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      06-19-2005
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".


 
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Dimitrios Tzortzakakis
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      06-19-2005
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$(E-Mail Removed)...
> 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



 
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Ken Wright
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      06-19-2005
jpeg isn't lossless, it's lossy, subject to the exceptions listed by the
others.

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


"Dimitrios Tzortzakakis" <(E-Mail Removed)> wrote in message
news:d94ieg$e2f$(E-Mail Removed)...
> 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$(E-Mail Removed)...
> > 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

>
>



 
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Ralf Schmode
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      06-19-2005
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.
However, there are operations - such as rotation by a multiple of 90
degrees - that can be carried out without *further* loss in comparision
to the JPEG input file.

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
 
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Paul Mitchum
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      06-19-2005
David J Taylor
<(E-Mail Removed)-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.
 
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Paul Mitchum
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      06-19-2005
Ralf Schmode <(E-Mail Removed)> 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.
 
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Ralf Schmode
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      06-19-2005
Paul Mitchum wrote:

> Ralf Schmode <(E-Mail Removed)> 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
 
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