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#11
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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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