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Do you use lossless JPEG recompression tools?



 
 
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  #11  
Old January 19th 08, 09:38 AM posted to rec.photo.digital
Ron Hunter
external usenet poster
 
Posts: 4,064
Default Do you use lossless JPEG recompression tools?

Sachin Garg wrote:
There are a number of tools available which can do "lossless"
compression of jpeg files, they get around 20-25% compression. There
are both commercial/proprietary (StufIt) and free/open-source options
(PackJPG, PAQ etc...).

Have you tried any such tool? Do you use any?

I am in process of publishing an image compression benchmark and want
to know what is in actual popular use and what all is only
academically interesting.

And if not, then why not? what do you think is missing in them that
would make you change your mind?

Sachin Garg [India]
www.sachingarg.com | www.c10n.info


JPEG and 'losless' are really mutually exclusive terms.
The whole idea of JPEG compression is to achieve high compression rates
(6:1 or better), by discarding information not required for satisfactory
image quality, and then applying a standard compression technique, such
as LZW with Huffman, to the result. Leaving out the lossy step results
in dramatically reduced compression. Not worth bothering with.
  #12  
Old January 19th 08, 04:05 PM posted to rec.photo.digital
Sachin Garg
external usenet poster
 
Posts: 79
Default Do you use lossless JPEG recompression tools?


On Jan 19, 12:57 pm, "David J Taylor" -
this-bit.nor-this-bit.co.uk wrote:
Sachin Garg wrote:

[]

Can I have any more opinions? Is anyone else here using these tools?


Not using - never seen any need.


OK.

btw, similar tools are possible for RAW files too, which are much
bigger than jpegs. Will such a lossless compression tool for raw
files, with 20-25% compression, be more useful?

Sachin Garg [India]
www.sachingarg.com | www.c10n.info
  #13  
Old January 19th 08, 04:09 PM posted to rec.photo.digital
Sachin Garg
external usenet poster
 
Posts: 79
Default Do you use lossless JPEG recompression tools?

On Jan 19, 1:38 pm, Ron Hunter wrote:
Sachin Garg wrote:
There are a number of tools available which can do "lossless"
compression of jpeg files, they get around 20-25% compression. There
are both commercial/proprietary (StufIt) and free/open-source options
(PackJPG, PAQ etc...).


Have you tried any such tool? Do you use any?


I am in process of publishing an image compression benchmark and want
to know what is in actual popular use and what all is only
academically interesting.


And if not, then why not? what do you think is missing in them that
would make you change your mind?


JPEG and 'losless' are really mutually exclusive terms.
The whole idea of JPEG compression is to achieve high compression rates
(6:1 or better), by discarding information not required for satisfactory
image quality, and then applying a standard compression technique, such
as LZW with Huffman, to the result. Leaving out the lossy step results
in dramatically reduced compression. Not worth bothering with.


You are correct that JPEG is lossy. These tools apply further lossless
compression on jpeg files.

Think of it as something similar to using zip.

Sachin Garg [India]
www.sachingarg.com | www.c10n.info
  #14  
Old January 19th 08, 04:14 PM posted to rec.photo.digital
David J Taylor[_4_]
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Posts: 1,151
Default Do you use lossless JPEG recompression tools?

Sachin Garg wrote:
On Jan 19, 12:57 pm, "David J Taylor" -
this-bit.nor-this-bit.co.uk wrote:
Sachin Garg wrote:

[]

Can I have any more opinions? Is anyone else here using these tools?


Not using - never seen any need.


OK.

btw, similar tools are possible for RAW files too, which are much
bigger than jpegs. Will such a lossless compression tool for raw
files, with 20-25% compression, be more useful?

Sachin Garg [India]


No, I would Zip or BZip or GZip. And I use RAW very little.

David


  #15  
Old January 19th 08, 04:27 PM posted to rec.photo.digital
John Navas[_2_]
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Posts: 3,956
Default Do you use lossless JPEG recompression tools?

On Sat, 19 Jan 2008 08:00:07 GMT, "David J Taylor"
wrote in
:

Sachin Garg wrote:
[]
This concern might be true for proprietary formats from unknown
companies, but is it really a concern when its an open-source solution
(or if its from a dependable company)?


Any proprietary format is dubious - look at the difficulties in reading
old word-processor formats. Open-source can be the kiss-of-death for a
project, as the programmers loose interest and move onto something else.
Seen that happen time after time.

Stick to standard JPEG.


My own advice is to save important images in lossless PNG format, which
preserves image quality with lossless compression, is widely accepted,
and is likely to be supported for a very long time to come. AFAIK, PNG
images can't be recompressed significantly.

JPEG-2000 is another option for lossless compression, but still has yet
to really catch on. And JPEG XR is coming, but still has a long way to
go.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)
  #16  
Old January 19th 08, 04:33 PM posted to rec.photo.digital
John Navas[_2_]
external usenet poster
 
Posts: 3,956
Default Do you use lossless JPEG recompression tools?

On Sat, 19 Jan 2008 02:38:40 -0600, Ron Hunter
wrote in :

Sachin Garg wrote:
There are a number of tools available which can do "lossless"
compression of jpeg files, they get around 20-25% compression. There
are both commercial/proprietary (StufIt) and free/open-source options
(PackJPG, PAQ etc...).

Have you tried any such tool? Do you use any?

I am in process of publishing an image compression benchmark and want
to know what is in actual popular use and what all is only
academically interesting.

And if not, then why not? what do you think is missing in them that
would make you change your mind?

Sachin Garg [India]
www.sachingarg.com | www.c10n.info


JPEG and 'losless' are really mutually exclusive terms.
The whole idea of JPEG compression is to achieve high compression rates
(6:1 or better), by discarding information not required for satisfactory
image quality, and then applying a standard compression technique, such
as LZW with Huffman, to the result. Leaving out the lossy step results
in dramatically reduced compression. Not worth bothering with.


quibble There are lossless and near-lossless variants of JPEG
(Lossless JPEG and JPEG-LS respectively), as well as lossless JPEG-2000.
See http://en.wikipedia.org/wiki/Lossless_JPEG All offer significant
compression. /quibble

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)
  #17  
Old January 19th 08, 04:55 PM posted to rec.photo.digital
John Navas[_2_]
external usenet poster
 
Posts: 3,956
Default Do you use lossless JPEG recompression tools?

On Sat, 19 Jan 2008 07:05:41 -0800 (PST), Sachin Garg
wrote in
:

On Jan 19, 12:57 pm, "David J Taylor" -
this-bit.nor-this-bit.co.uk wrote:
Sachin Garg wrote:

[]

Can I have any more opinions? Is anyone else here using these tools?


Not using - never seen any need.


OK.

btw, similar tools are possible for RAW files too, which are much
bigger than jpegs. Will such a lossless compression tool for raw
files, with 20-25% compression, be more useful?


RAW formats are proprietary to particular products, and thus unsuitable
for archival storage. Adobe DNG is a better alternative that has
compression built-in, probably not recompressible.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)
  #18  
Old January 19th 08, 04:57 PM posted to rec.photo.digital
John Navas[_2_]
external usenet poster
 
Posts: 3,956
Default Do you use lossless JPEG recompression tools?

On Sat, 19 Jan 2008 07:09:48 -0800 (PST), Sachin Garg
wrote in
:

On Jan 19, 1:38 pm, Ron Hunter wrote:


JPEG and 'losless' are really mutually exclusive terms.
The whole idea of JPEG compression is to achieve high compression rates
(6:1 or better), by discarding information not required for satisfactory
image quality, and then applying a standard compression technique, such
as LZW with Huffman, to the result. Leaving out the lossy step results
in dramatically reduced compression. Not worth bothering with.


You are correct that JPEG is lossy. These tools apply further lossless
compression on jpeg files.

Think of it as something similar to using zip.


I think his point is that lossy compression isn't a good choice for
archival storage in the first place.

--
Best regards,
John Navas
Panasonic DMC-FZ8 (and several others)
  #19  
Old January 19th 08, 04:59 PM posted to rec.photo.digital
David J Taylor[_4_]
external usenet poster
 
Posts: 1,151
Default Do you use lossless JPEG recompression tools?

John Navas wrote:
[]
My own advice is to save important images in lossless PNG format,
which preserves image quality with lossless compression, is widely
accepted, and is likely to be supported for a very long time to come.
AFAIK, PNG images can't be recompressed significantly.


Agreed, with the proviso that if you are /starting/ with a JPEG image,
downloaded from the camera or flash-card for example, the only point in
converting it for saving as PNG would be if you consider PNG a more robust
saving format. Otherwise, conversion will simply loose the metadata from
the JPEG file.

Cheers,
David


  #20  
Old January 19th 08, 05:29 PM posted to rec.photo.digital
Sachin Garg
external usenet poster
 
Posts: 79
Default Do you use lossless JPEG recompression tools?


On Jan 19, 8:57 pm, John Navas wrote:
On Sat, 19 Jan 2008 07:09:48 -0800 (PST), Sachin Garg
wrote in
:

On Jan 19, 1:38 pm, Ron Hunter wrote:
JPEG and 'losless' are really mutually exclusive terms.
The whole idea of JPEG compression is to achieve high compression rates
(6:1 or better), by discarding information not required for satisfactory
image quality, and then applying a standard compression technique, such
as LZW with Huffman, to the result. Leaving out the lossy step results
in dramatically reduced compression. Not worth bothering with.


You are correct that JPEG is lossy. These tools apply further lossless
compression on jpeg files.


Think of it as something similar to using zip.


I think his point is that lossy compression isn't a good choice for
archival storage in the first place.


Ah, I thought he misunderstood what these tools do :-)

But anyway, that mostly depends on what one wants more (quality and
ability to do good post-processing, or just small good-enough files)
and most of the time we just don't get the choice (most cameras do
jpeg only).

In general however, I agree that loss should be avoided wherever
possible.

Sachin Garg [India]
www.sachingarg.com | www.c10n.info
 




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