jpeg compression
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This discussion has really helped me understand some more things about file formats.
So if i'm only taking into the account picture quality and flexibility and don't care about metadata tiff is better than png for editing right ? On 6/29/07, Gilles Caulier <[hidden email]> wrote:
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Re: jpeg compression
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Am Freitag 29 Juni 2007 schrieb Hugo Palma:
> This discussion has really helped me understand some more things about file > formats. > > So if i'm only taking into the account picture quality and flexibility and > don't care about metadata tiff is better than png for editing right ? > No :-) TIFF is a very flexible but also complicate container for image data. This flexibility is the reason that many raw formats are based on TIFF internal directory structures but this leads also to the problem that a library like libtiff can not cope with every special vendor solution. PNG is simple and has everything you need for storing an image. To keep it simple in PNG you can e.g. not handle CYMK (print) or real number based (HDR) image data nor handle multiple images in one file. But being simple PNG often has better compression ratio than standard TIFF. To make it short: Only looking at lossless storing images to a file TIFF and PNG are equal. But digiKam has better PNG support compared to TIFF as the used PNG libraries are simply better than the free and open tiff libs. So, for long time storage today PNG is the way to go as it preserves the metadata if the image. This may change in the future when TIFF-based DNG-format gets better support. ;-) HTH Thorsten _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Would it make sense to put a brief summary of the contents of this
thread into a FAQ entry (eg. "Which image format should I choose?")? If yes, Bjorn, could you maybe set up a short text, which I could then put into the FAQ on the digikam homepage? Alternatively, is there anything which should be added to handbook, which already has a detailed account on image formats, see http://docs.kde.org/development/en/extragear-graphics/digikam/using-fileformatsupport.html ? Best, Arnd _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Bugzilla from thorsten.schnebeck@gmx.net
2007/6/30, Thorsten Schnebeck <[hidden email]>: Am Freitag 29 Juni 2007 schrieb Hugo Palma: Ah the famous DNG format... To have studied it indeep, i can said than : DNG == TIFF + new tag. DNG is now an ISO standard (i have seen a message about it into libtiff ML) DNG is limited to store image data in 2 way : the first is a pseudo lossless JPEG compression supporting 16 bits color depth (in fact JPEG algorith with compression level set to 100, but supporting 16 bits/color/pixels). The compression ratio is good, but it still JPEG stuff... This way is used by all camera which support DNG as well, and not the second way... DNG support only a _real_ lossless image data storage, which is in fact the linear 16 raw image data. DNG do not support the famous Adobe Deflate compression algorithm provide by TIFF file format. It really stupid... This one give the equivalent compression ratio results of PNG. If you try to use DNG converter from Adobe, and you use the RAW linear storage of image data, the DNG file will be huge ! For me DNG do not give any advantages against PNG... Gilles HTH _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
Re: jpeg compression
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Hi,
> To have studied it indeep, i can said than : > > DNG == TIFF + new tag. > DNG is now an ISO standard (i have seen a message about it into libtiff ML) > DNG is limited to store image data in 2 way : the first is a pseudo > lossless JPEG compression supporting 16 bits color depth (in fact JPEG > algorith with compression level set to 100, but supporting 16 > bits/color/pixels). The compression ratio is good, but it still JPEG > stuff... This is IMHO wrong. You mix up an image format with the Joint Photographic Experts Group. DNG uses JPEG lossless huffman: http://en.wikipedia.org/wiki/Lossless_JPEG or deeper: http://www.hpl.hp.com/loco/HPL-98-193R1.pdf > This way is used by all camera which support DNG as well, and not > the second way... > DNG support only a _real_ lossless image data storage, which is in fact the > linear 16 raw image data. DNG do not support the famous Adobe Deflate > compression algorithm provide by TIFF file format. It really stupid... This > one give the equivalent compression ratio results of PNG. If you try to use > DNG converter from Adobe, and you use the RAW linear storage of image data, > the DNG file will be huge ! The linear 16bit raw converted data is not recommended. I found this thread which helps to understand some DNG (fallback) concepts: (from: http://www.adobeforums.com/cgi-bin/webx/.3bc0d8de) > > goodlux - 2:31am Feb 26, 07 PST (#14 of 15) > > ============================= > > I wish this information was presented by Adobe in a clearer fashion, > > perhaps in the help menu for the Converter itself. > > > > Users should be given a little more information so they can understand > > some of the implications of using the various options that the converter > > presents. > > > > For instance: it is helpful for a user to know that if they create a .dng > > file and embed the raw file, and create a full-sized preview, that they > > will end up with a file that is double the size of the original raw file. > > So if they convert all their raw files this way, they will need double > > the space. > > > > Also, I'm not clear at all about the whole "preserve raw image" vs > > "convert to linear image" option at all. Why would a use want to do one > > or the other? What are the pros and cons? > > > > Same thing about Lossless compression...why wouldn't someone want > > lossless compression? Is there a performance hit? How much of a > > difference does this compression usually make? > > > > I came across this post because I have the same question as the original > > poster. > > > > How is it possible that a .dng file is smaller than the original raw > > (.cr2) file? A .cr2 file is already compressed with lossless > > compression...and that compression is fairly state of the art. How is it > > possible that .dng can do it better? There must be some data getting > > thrown out in the conversion...or else you wouldn't have the option of > > embedding the raw file. So what is getting thrown out? How important is > > it? I'm particularly concerned with Canon files. > > > > Does anyone have some solid, knowledgeable information? > > > > ************************************************************************** > > > > Barry Clive Pearson - 8:10am Feb 26, 07 PST (#15 of 15) > > ==================================== > > "Also, I'm not clear at all about the whole "preserve raw image" vs > > "convert to linear image" option at all. Why would a use want to do one > > or the other? What are the pros and cons?" By default, this is "don't > > convert", and that is right. Converting it means doing a raw conversion, > > which means that later products don't get their own chance to do it. (It > > also results in a bigger file). > > > > Sometimes products can handle "linear DNGs" but not the unconverted DNGs. > > For example, I've known products that can't handle the unconverted data > > from a Fujifilm camera, but could handle the Linear version, so in that > > case converting was the only way to get the file processed by that > > product. > > > > "Same thing about Lossless compression...why wouldn't someone want > > lossless compression? Is there a performance hit? How much of a > > difference does this compression usually make?" I think there have been > > products that couldn't uncompress DNG files, but that doesn't appear to > > be common. So normally compressed DNG is good. > > > > "How is it possible that a .dng file is smaller than the original raw > > (.cr2) file? A .cr2 file is already compressed with lossless > > compression...and that compression is fairly state of the art. How is it > > possible that .dng can do it better?" DNG just does it a little better! > > (In fact, CR2 and DNG both use the same type of lossless compression, but > > there appears to be different levels of compression, perhaps because DNG > > tiles it in a way that optimises compression?) > > > > DNG files from CR2s should hold a superset, not a subset, of what is CR2 > > files. > For me DNG do not give any advantages against PNG... > > Gilles The main difference is that DNG can keep the mosaiced representation of the sensor in the image data. Together with new standard and open metatags you can use future raw converter techniques with your original sensor data. In PNG the image representation is already RGB ordered. This handles (in http://www.adobe.com/products/dng/pdfs/dng_spec.pdf ) the "PhotometricInterpretation" metatag. When the spec speaks from CFA they mean Color Filter Array - this is the sensor pattern. DNG is not that evil ;-) HTH Thorsten _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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2007/6/30, Thorsten Schnebeck <[hidden email]>: Hi, Perhaps, but in DNG, if you records original CFA data from original RAW file + the decode image in JPEG format, you have a huge file ! DNG It's not a revolution for me... Gilles HTH _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
Re: jpeg compression
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> > DNG is not that evil ;-)
> > Perhaps, but in DNG, if you records original CFA data from original RAW > file + the decode image in JPEG format, you have a huge file ! I don't understand? Why do you want to store both? As you can read in the copied thread the DNG file is shorter than a original CR2 raw. > DNG It's not a revolution for me... DNG can be an standard for raw files same like pdf is now for text presentations. I don't know any other raw file format with open specs. Its better than all the proprietary raw stuff of the camera vendors. Its up to the license experts if there can exist a GPL libdng due to Adobe patent or if only a free dng-app is possible. As in e.g. kpdf is also a notice that grants Adobe the copyright for pdf data and structures I don't think this is a problem now - but GPL3 raised today ;-) Bye Thorsten _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Arnd Baecker
Lørdag 30 juni 2007 18:34, skrev Arnd Baecker:
> Would it make sense to put a brief summary of the contents of this > thread into a FAQ entry (eg. "Which image format should I choose?")? > > If yes, Bjorn, could you maybe set up a short text, which > I could then put into the FAQ on the digikam homepage? > Hi Arnd I was about to start writing a small piece, but discovered something unfortunate when prepping this week's holiday photos from Berlin and Potsdam: I used the Digikam batch process to convert the jpeg files from my Nikon D40 to png, and found that all the exif data were lost during conversion. I also took a few photos with my digital VCR camera, but these images did not loose the exif data. Strange? When I opened a jpeg file from the D40 in the editor and saved it as a png, the exif data were also *not* lost. I have Digkam 0.9.0. I'll experiment further and finally send you a small piece for the faq. -Bjorn > Alternatively, is there anything which should be added to > handbook, which already has a detailed account on image formats, see > http://docs.kde.org/development/en/extragear-graphics/digikam/using-filefor >matsupport.html ? > > Best, Arnd > _______________________________________________ > Digikam-users mailing list > [hidden email] > https://mail.kde.org/mailman/listinfo/digikam-users Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Hi Bjoern,
On Sat, 7 Jul 2007, [iso-8859-1] Bjørn Kvisli wrote: > Lørdag 30 juni 2007 18:34, skrev Arnd Baecker: > > Would it make sense to put a brief summary of the contents of this > > thread into a FAQ entry (eg. "Which image format should I choose?")? > > > > If yes, Bjorn, could you maybe set up a short text, which > > I could then put into the FAQ on the digikam homepage? > > > Hi Arnd > I was about to start writing a small piece, but discovered something > unfortunate when prepping this week's holiday photos from Berlin and Potsdam: > I used the Digikam batch process to convert the jpeg files from my Nikon D40 > to png, and found that all the exif data were lost during conversion. I also > took a few photos with my digital VCR camera, but these images did not loose > the exif data. Strange? When I opened a jpeg file from the D40 in the editor > and saved it as a png, the exif data were also *not* lost. I have Digkam > 0.9.0. Sounds like a bug (or non-feature) to me. You could try with 0.9.2, but I am not sure if anything was done in that part ... Not sure, but maybe you should file a bug report, if there is no further input on this in the next days Best, Arnd _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Lørdag 07 juli 2007 23:56, skrev Arnd Baecker:
> Hi Bjoern, > > On Sat, 7 Jul 2007, [iso-8859-1] Bjørn Kvisli wrote: > > Lørdag 30 juni 2007 18:34, skrev Arnd Baecker: > > > Would it make sense to put a brief summary of the contents of this > > > thread into a FAQ entry (eg. "Which image format should I choose?")? > > > > > > If yes, Bjorn, could you maybe set up a short text, which > > > I could then put into the FAQ on the digikam homepage? > > > > Hi Arnd > > I was about to start writing a small piece, but discovered something > > unfortunate when prepping this week's holiday photos from Berlin and > > Potsdam: I used the Digikam batch process to convert the jpeg files from > > my Nikon D40 to png, and found that all the exif data were lost during > > conversion. I also took a few photos with my digital VCR camera, but > > these images did not loose the exif data. Strange? When I opened a jpeg > > file from the D40 in the editor and saved it as a png, the exif data > > were also *not* lost. I have Digkam 0.9.0. > > Sounds like a bug (or non-feature) to me. > You could try with 0.9.2, but I am not sure if anything was > done in that part ... I'm not sure if I manage to install 0.9.2 on Kubuntu Dapper. > Not sure, but maybe you should file a bug report, > if there is no further input on this in the next days > > Best, Arnd > _______________________________________________ > Digikam-users mailing list > [hidden email] > https://mail.kde.org/mailman/listinfo/digikam-users _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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On Sun, 8 Jul 2007, [iso-8859-1] Bjørn Kvisli wrote: > Lørdag 07 juli 2007 23:56, skrev Arnd Baecker: > > Hi Bjoern, > > > > On Sat, 7 Jul 2007, [iso-8859-1] Bjørn Kvisli wrote: > > > Lørdag 30 juni 2007 18:34, skrev Arnd Baecker: > > > > Would it make sense to put a brief summary of the contents of this > > > > thread into a FAQ entry (eg. "Which image format should I choose?")? > > > > > > > > If yes, Bjorn, could you maybe set up a short text, which > > > > I could then put into the FAQ on the digikam homepage? > > > > > > Hi Arnd > > > I was about to start writing a small piece, but discovered something > > > unfortunate when prepping this week's holiday photos from Berlin and > > > Potsdam: I used the Digikam batch process to convert the jpeg files from > > > my Nikon D40 to png, and found that all the exif data were lost during > > > conversion. I also took a few photos with my digital VCR camera, but > > > these images did not loose the exif data. Strange? When I opened a jpeg > > > file from the D40 in the editor and saved it as a png, the exif data > > > were also *not* lost. I have Digkam 0.9.0. > > > > Sounds like a bug (or non-feature) to me. > > You could try with 0.9.2, but I am not sure if anything was > > done in that part ... > > I'm not sure if I manage to install 0.9.2 on Kubuntu Dapper. might be easier to upgrade ;-) (I know never stop a running system - so don't blame me if it breaks ...) Good luck, Arnd _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Arnd Baecker
Lørdag 30 juni 2007 18:34, skrev Arnd Baecker:
> Would it make sense to put a brief summary of the contents of this > thread into a FAQ entry (eg. "Which image format should I choose?")? > > If yes, Bjorn, could you maybe set up a short text, which > I could then put into the FAQ on the digikam homepage? > Arnd, the attached file contains a short text on which file format to use. I am fairly new to this, so please change it as you see necessary if you decide to use it for the FAQ. I did not write anything about the RAW format. The reason is that I could not find a good way to use it with Digikam. I could import the RAW files (nef files) from my Nikon D40 and edit them, but not save them. When trying to convert them to jpeg, I only got a file of about 961 kb without exif data. It seems like conversion from RAW to tiff worked, but most of the exif data were lost. Has anyone else experience with the RAW files from Nikon D40? Reagrds, Bjørn > Alternatively, is there anything which should be added to > handbook, which already has a detailed account on image formats, see > http://docs.kde.org/development/en/extragear-graphics/digikam/using-filefor >matsupport.html ? > > Best, Arnd > _______________________________________________ > Digikam-users mailing list > [hidden email] > https://mail.kde.org/mailman/listinfo/digikam-users _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Hi,
Batch converting jpegs from the camera to pngs sounds interesting. What level of png compression would people reccomend ? Cheers F --------------------------------------------------------------------- - - - - - - The information in this e-mail and any attachments is confidential and is intended for the attention and use of the named addressee(s). It must not be disclosed to any other person without our authority. If you are not the intended recipient, or a person responsible for delivering it to the intended recipient or are aware that this e-mail has been sent to you in error, you are not authorised to and must not disclose, copy, distribute, or retain this message or any part of it. We sweep all outgoing messages for the presence of computer viruses. However, we cannot accept any responsibility for any loss or damage to your systems due to viruses or malicious code not detected. The statements and opinions expressed in this message are those of the author and do not necessarily reflect those of the organisations within the Cornwall & Isles of Scilly Health Community. This email may be disclosed under the Freedom of Information Act 2000 or the Environmental Information Regulations 2004. --------------------------------------------------------------------- - - - - - - _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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On Friday 03 August 2007, Francesco Scaglioni wrote:
> Hi, > > Batch converting jpegs from the camera to pngs sounds > interesting. What level of png compression would people > reccomend ? As it's lossless, the only tradeoff is disk space versus CPU time consumption. -- Best regards, Jakob Oestergaard _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
Re: jpeg compression
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Jakob Østergaard wrote:
> As it's lossless, the only tradeoff is disk space versus CPU time > consumption. Keep in mind, however, that the compression option label is somewhat misleading - you get the smallest file when the compression level is set to lowest value instead of highest. Paweł _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Arnd Baecker
Hi,
> This suggests, that maybe something like 70 was used inside of the camera? > > From the number of pixels Nx * Ny, the number of bytes needed > to store the image (without) compression should follow from > Nx * Ny * (8+8+8), i.e. one Byte per R, G, B. On a resolution of 3264 x 2448 I get jpeg file sizes of between 2.2 and 4 MB per image (subject matter depending). 3264 x 2448 x 24 = 191,766,528 For a particular image of size 3,974,526 (size and resolution stated by digikam) the compression facto does not make sense to me (in that I don't fully understand ). A factor of 48 cannot be possible : surely. Any suggestions ? Regards, Francesco --------------------------------------------------------------------- - - - - - - The information in this e-mail and any attachments is confidential and is intended for the attention and use of the named addressee(s). It must not be disclosed to any other person without our authority. If you are not the intended recipient, or a person responsible for delivering it to the intended recipient or are aware that this e-mail has been sent to you in error, you are not authorised to and must not disclose, copy, distribute, or retain this message or any part of it. We sweep all outgoing messages for the presence of computer viruses. However, we cannot accept any responsibility for any loss or damage to your systems due to viruses or malicious code not detected. The statements and opinions expressed in this message are those of the author and do not necessarily reflect those of the organisations within the Cornwall & Isles of Scilly Health Community. This email may be disclosed under the Freedom of Information Act 2000 or the Environmental Information Regulations 2004. --------------------------------------------------------------------- - - - - - - _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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You are computing the uncompressed size of your image incorrectly.
What you have computed is the number of bits needed to store the image. You most likely want the number of bytes. There is an 8-fold difference. For an uncompressed 24 bit image, each pixel takes up 3 bytes, therefore: 3264 x 2448 x 3 = 23,970,816 bytes If digikam reports a compressed size of 3,974,526, then that's a 6x compression factor, which sounds reasonable. -w On 8/21/07, Francesco Scaglioni <[hidden email]> wrote: > Hi, > > > This suggests, that maybe something like 70 was used inside of the camera? > > > > From the number of pixels Nx * Ny, the number of bytes needed > > to store the image (without) compression should follow from > > Nx * Ny * (8+8+8), i.e. one Byte per R, G, B. > > On a resolution of 3264 x 2448 I get jpeg file sizes of between > 2.2 and 4 MB per image (subject matter depending). > > 3264 x 2448 x 24 = 191,766,528 > > For a particular image of size 3,974,526 (size and > resolution stated by digikam) the compression facto does not > make sense to me (in that I don't fully understand ). A > factor of 48 cannot be possible : surely. > > Any suggestions ? > > Regards, > > Francesco > > --------------------------------------------------------------------- > - > - > - > - > - > - > The information in this e-mail and any attachments is confidential > and > is > intended for the attention and use of the named addressee(s). It > must > not > be disclosed to any other person without our authority. If you are > not > the intended recipient, or a person responsible for delivering it to > the > intended recipient or are aware that this e-mail has been sent to > you > in > error, you are not authorised to and must not disclose, copy, > distribute, > or retain this message or any part of it. > > We sweep all outgoing messages for the presence of computer viruses. > However, we cannot accept any responsibility for any loss or damage > to > your systems due to viruses or malicious code not detected. > > The statements and opinions expressed in this message are those of > the > author and do not necessarily reflect those of the organisations > within > the Cornwall & Isles of Scilly Health Community. > > This email may be disclosed under the Freedom of Information Act > 2000 > or > the Environmental Information Regulations 2004. > --------------------------------------------------------------------- > - > - > - > - > - > - > _______________________________________________ > Digikam-users mailing list > [hidden email] > https://mail.kde.org/mailman/listinfo/digikam-users > Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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