jpeg compression
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Hi
I had set up Digikam with 100% jpeg quality, and I found that the files got very big when I saved them after editing. Is it possible to say what is a resonable value for this setting? I use a Nikon D40 Regards, Bjorn _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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75 quality setting is a good value, used every where.
Gilles 2007/6/27, Bjørn Kvisli <[hidden email]>: Hi _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Bjørn Kvisli
Arnd,
I took an image out of the camera ( a Kodak C40, this time) and saved it with different values for jpeg quality. The orginal file was 1.2 MB big, and here are the sizes with diffrerent levels of jpeg quality: 75 -> 1.3 MB 85 -> 1.8 MB 90 -> 1.9 MB 92 -> 2.3 MB 95 -> 2.6 MB 97 -> 3.2 MB 100 -> 4.5 MB All of them bigger than the original file. I don't thimk I understand this. -Bjørn _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Arnd,
One more thing I discovered. The Gimp makes smaller jpeg files than Digikam with the same levels of jpeg quality: 100: 2.9MB (Digikam 4.5), 75: 1.1 MB (Digikam 1.3) Torsdag 28 juni 2007 16:16, skrev Bjørn Kvisli: > Arnd, > > I took an image out of the camera ( a Kodak C40, this time) and saved it > with different values for jpeg quality. The orginal file was 1.2 MB big, > and here are the sizes with diffrerent levels of jpeg quality: > > 75 -> 1.3 MB > 85 -> 1.8 MB > 90 -> 1.9 MB > 92 -> 2.3 MB > 95 -> 2.6 MB > 97 -> 3.2 MB > 100 -> 4.5 MB > > All of them bigger than the original file. I don't thimk I understand this. > -Bjørn > _______________________________________________ > 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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In reply to this post by Bjørn Kvisli
On Thu, 28 Jun 2007, [iso-8859-1] Bjørn Kvisli wrote: > Arnd, > > I took an image out of the camera ( a Kodak C40, this time) and saved it with > different values for jpeg quality. The orginal file was 1.2 MB big, and here > are the sizes with diffrerent levels of jpeg quality: > > 75 -> 1.3 MB > 85 -> 1.8 MB > 90 -> 1.9 MB > 92 -> 2.3 MB > 95 -> 2.6 MB > 97 -> 3.2 MB > 100 -> 4.5 MB > > All of them bigger than the original file. I don't thimk I understand this. 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. What is the resolution of your camera? Anyway, overall the above looks pretty reasonable to me. Best, Arnd _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Torsdag 28 juni 2007 16:31, skrev Arnd Baecker:
> On Thu, 28 Jun 2007, [iso-8859-1] Bjørn Kvisli wrote: > > Arnd, > > > > I took an image out of the camera ( a Kodak C40, this time) and saved it > > with different values for jpeg quality. The orginal file was 1.2 MB big, > > and here are the sizes with diffrerent levels of jpeg quality: > > > > 75 -> 1.3 MB > > 85 -> 1.8 MB > > 90 -> 1.9 MB > > 92 -> 2.3 MB > > 95 -> 2.6 MB > > 97 -> 3.2 MB > > 100 -> 4.5 MB > > > > All of them bigger than the original file. I don't thimk I understand > > this. > > This suggests, that maybe something like 70 was used inside of the camera? If I understand this right, assuming that the Kodac C340 uses jpeg quality of 70 internally, it makes no sense to set a higher value in Digikam? Hm.. I must find out what kind of compression my Nikon uses. > > >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. > > What is the resolution of your camera? The resolution is 2576x1932 (4.98Mpx) > > Anyway, overall the above looks pretty reasonable to me. > > 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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In reply to this post by Bjørn Kvisli
2007/6/28, Bjørn Kvisli <[hidden email]>: Arnd, Gimp and digiKam jpeg compression level range are different. digikam is more like photoshop stuff. Also in digiKam i have set 2 options to optimize the quality instead the size of files... This is why you can see diff... Gilles _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Bjørn Kvisli
On Donnerstag, 28. Juni 2007, Bjørn Kvisli wrote:
> If I understand this right, assuming that the Kodac C340 uses jpeg quality > of 70 internally, it makes no sense to set a higher value in Digikam? it still makes sense, because every new save looses some more information. Although its not that dramatic in reality, you could think of percents just to better understand: then if you save the 70% with 100% you get 70% again, if you save it with 70% you get only 49% (70% of 70%) and so on. I found that a jpg value of 88 in digiKam gives approx. same results as 80 in photoshop (in quality and size). That's the value I use for my web pics. However, as long as you work with the pictures better use a lossless file format and only save the final pictures to .jpg (if at all). And leave the originals untouched. kind regards Daniel -- Daniel Bauer photographer Basel Switzerland professional photography: http://www.daniel-bauer.com erotic art photos: http://www.bauer-nudes.com/en/linux.html Madagascar special: http://www.sanic.ch _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
Re: jpeg compression
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Dnia czwartek 28 czerwiec 2007, Daniel Bauer napisał:
> On Donnerstag, 28. Juni 2007, Bj?rn Kvisli wrote: > > If I understand this right, assuming that the Kodac C340 uses jpeg > > quality of 70 internally, it makes no sense to set a higher value in > > Digikam? > > it still makes sense, because every new save looses some more > information. Although its not that dramatic in reality, you could think > of percents just to better understand: then if you save the 70% with > 100% you get 70% again, if you save it with 70% you get only 49% (70% of > 70%) and so on. AFAIU JPEG this is not exactly true. Quality is level of losing information. After saving to 70 you lost all information above that and next savings to 70 shouldn't cause losing of more detail. Note however that different implementations may differ and 70 level in one program isn't exactly the same 70 in another. m. _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Gilles Caulier-4
Torsdag 28 juni 2007 18:13, skrev Gilles Caulier:
> 2007/6/28, Bjørn Kvisli <[hidden email]>: > > Arnd, > > One more thing I discovered. The Gimp makes smaller jpeg files than > > Digikam > > with the same levels of jpeg quality: 100: 2.9MB (Digikam 4.5), 75: 1.1 > > MB (Digikam 1.3) > > Gimp and digiKam jpeg compression level range are different. digikam is > more like photoshop stuff. > > Also in digiKam i have set 2 options to optimize the quality instead the > size of files... > > This is why you can see diff... > > Gilles _______________________________________________ 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 mikmach@wp.pl
Torsdag 28 juni 2007 19:01, skrev Mikolaj Machowski:
> Dnia czwartek 28 czerwiec 2007, Daniel Bauer napisał: > > On Donnerstag, 28. Juni 2007, Bj?rn Kvisli wrote: > > > If I understand this right, assuming that the Kodac C340 uses jpeg > > > quality of 70 internally, it makes no sense to set a higher value in > > > Digikam? > > > > it still makes sense, because every new save looses some more > > information. Although its not that dramatic in reality, you could think > > of percents just to better understand: then if you save the 70% with > > 100% you get 70% again, if you save it with 70% you get only 49% (70% of > > 70%) and so on. > > AFAIU JPEG this is not exactly true. Quality is level of losing > information. After saving to 70 you lost all information above that and > next savings to 70 shouldn't cause losing of more detail. Well, I really hope this is the case. Loosing detail with each save would really be bad. -Bjørn > > Note however that different implementations may differ and 70 level in > one program isn't exactly the same 70 in another. > > m. > > _______________________________________________ > 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 Thu, 28 Jun 2007, [utf-8] Bjørn Kvisli wrote:
[...] > Well, I really hope this is the case. Loosing detail with each save would > really be bad. Have a look at http://www.cywarp.com/faq_jpg_degradation.htm (Of course best is to try it out ... ;-) So if this is important for you, then a) use png to save edited pictures b) if you really aim at best quality, then start with raw images However, then you should not worry too much about file sizes, they are just as big as they are .... ;-) Best, Arnd _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Torsdag 28 juni 2007 20:24, skrev Arnd Baecker:
> On Thu, 28 Jun 2007, [utf-8] Bjørn Kvisli wrote: > > [...] > > > Well, I really hope this is the case. Loosing detail with each save would > > really be bad. > > Have a look at > http://www.cywarp.com/faq_jpg_degradation.htm > (Of course best is to try it out ... ;-) > degradation as descibed in the linked article. I guess I have to find out more about this. Digikam also has a setting for png compression. Mine is set to 9 (maximum). Is png still lossless? > So if this is important for you, then > a) use png to save edited pictures > b) if you really aim at best quality, then start with raw images > However, then you should not worry too much about > file sizes, they are just as big as they are .... ;-) > > 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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2007/6/28, Bjørn Kvisli <[hidden email]>: Torsdag 28 juni 2007 20:24, skrev Arnd Baecker: yes, PNG is always lossless (zip like), as TIFF compression do (deflate) : http://en.wikipedia.org/wiki/Png Note : unlike wikipedia said, PNG support Exif, IPTC, and XMP as well. Digikam full support Exif/Iptc with PNG, as ImageMagick or Exiftool can do. Gilles _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Daniel Bauer-2
Torsdag 28 juni 2007 18:20, skrev Daniel Bauer:
> On Donnerstag, 28. Juni 2007, Bjørn Kvisli wrote: > > If I understand this right, assuming that the Kodac C340 uses jpeg > > quality of 70 internally, it makes no sense to set a higher value in > > Digikam? > > it still makes sense, because every new save looses some more information. > Although its not that dramatic in reality, you could think of percents just > to better understand: then if you save the 70% with 100% you get 70% again, > if you save it with 70% you get only 49% (70% of 70%) and so on. > The article linked below says the same as you. I have to be carefull when using jpegs, I guess. http://graphicssoft.about.com/od/formatsjpeg/a/jpegmythsfacts.htm > I found that a jpg value of 88 in digiKam gives approx. same results as 80 > in photoshop (in quality and size). That's the value I use for my web pics. > > However, as long as you work with the pictures better use a lossless file > format and only save the final pictures to .jpg (if at all). And leave the > originals untouched. > > kind regards > > Daniel Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
Re: jpeg compression
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In reply to this post by Arnd Baecker
Dnia czwartek 28 czerwiec 2007, Arnd Baecker napisał:
> On Thu, 28 Jun 2007, [utf-8] Bj?rn Kvisli wrote: > > [...] > > > Well, I really hope this is the case. Loosing detail with each save > > would really be bad. > > Have a look at > http://www.cywarp.com/faq_jpg_degradation.htm > (Of course best is to try it out ... ;-) Tried it and looks like I wasn't right. However - on that page they have completely f*cked up jpg library. I tried to do that in Digikam (12 steps - rotate, save in IE) and in ImageMagick (100 steps inside of while loop - jpg -> png -> jpg with quality 75) and loss of quality was barely visible. m. _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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In reply to this post by Daniel Bauer-2
On Thursday 28 June 2007 18:20:43 Daniel Bauer wrote:
> On Donnerstag, 28. Juni 2007, Bjørn Kvisli wrote: > > If I understand this right, assuming that the Kodac C340 uses jpeg > > quality of 70 internally, it makes no sense to set a higher value in > > Digikam? > > it still makes sense, because every new save looses some more information. > Although its not that dramatic in reality, you could think of percents just > to better understand: then if you save the 70% with 100% you get 70% again, > if you save it with 70% you get only 49% (70% of 70%) and so on. > > I found that a jpg value of 88 in digiKam gives approx. same results as 80 > in photoshop (in quality and size). That's the value I use for my web pics. > > However, as long as you work with the pictures better use a lossless file > format and only save the final pictures to .jpg (if at all). And leave the > originals untouched. A tip; When order paper photos from my digital images at the local shop (which uses a Fujicolor service which means the actual paper photos get developed somewhere in germany then shipped back to .dk so I can pick them up at the local shop), I found that JPEG images are a lot better than uncompressed TIFF. It turns out, that if I deliver TIFFs, the "clever" kiosk system will convert them (most likely to JPEG) with a pretty heavy compression. If I deliver JPEGs (at 95% quality) the images are not further compressed, and they look crisp and sharp on paper. I tried a test run with several different pictures, two copies of each picture (one JPEG one TIFF), and the TIFFs were very noticeably "smudged" or "blurred", suffering the artifacts of a heavy JPEG compression (or other compression that cuts out high frequencies). That's one case where I've found JPEGs to be superior to TIFFs, although not for the reasons one would usually expect ;) -- Jakob Østergaard _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Torsdag 28 juni 2007 23:09, skrev Jakob Østergaard:
> On Thursday 28 June 2007 18:20:43 Daniel Bauer wrote: > > On Donnerstag, 28. Juni 2007, Bjørn Kvisli wrote: > > > If I understand this right, assuming that the Kodac C340 uses jpeg > > > quality of 70 internally, it makes no sense to set a higher value in > > > Digikam? > > > > it still makes sense, because every new save looses some more > > information. Although its not that dramatic in reality, you could think > > of percents just to better understand: then if you save the 70% with 100% > > you get 70% again, if you save it with 70% you get only 49% (70% of 70%) > > and so on. > > > > I found that a jpg value of 88 in digiKam gives approx. same results as > > 80 in photoshop (in quality and size). That's the value I use for my web > > pics. > > > > However, as long as you work with the pictures better use a lossless file > > format and only save the final pictures to .jpg (if at all). And leave > > the originals untouched. > > A tip; > > When order paper photos from my digital images at the local shop (which > uses a Fujicolor service which means the actual paper photos get developed > somewhere in germany then shipped back to .dk so I can pick them up at the > local shop), I found that JPEG images are a lot better than uncompressed > TIFF. > > It turns out, that if I deliver TIFFs, the "clever" kiosk system will > convert them (most likely to JPEG) with a pretty heavy compression. If I > deliver JPEGs (at 95% quality) the images are not further compressed, and > they look crisp and sharp on paper. > > I tried a test run with several different pictures, two copies of each > picture (one JPEG one TIFF), and the TIFFs were very noticeably "smudged" > or "blurred", suffering the artifacts of a heavy JPEG compression (or other > compression that cuts out high frequencies). > > That's one case where I've found JPEGs to be superior to TIFFs, although > not for the reasons one would usually expect ;) Interesting! I'll probably do as you in the futures. keep my images in a lossless format and convert to jpg before sending them off to the print shop. Now, I've heard about two lossless formats here on the mailing list: tiff and png. Which one is bes to use with Digikam? It seems like you keep all the exif data with png, but lose them with tiff. -Bjørn _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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Actually, I believe it is the other way around. PNG destroys EXIF metadata, while TIFF keeps it intact. As for which to use, it really depends. I tend to use TIFF because it can support other color spaces and greater bit depth (as I shoot RAW).
On 6/28/07, Bjørn Kvisli <[hidden email]> wrote: Torsdag 28 juni 2007 23:09, skrev Jakob Østergaard: _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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2007/6/29, Liquiddoom <[hidden email]>: Actually, I believe it is the other way around. PNG destroys EXIF metadata, Completly wrong !!! PNG support Exif, makernote, Iptc, Xmp. In digiKam it's fully supported as well Just try a simple test using ImageMagick with a JPEG file which have Exif and IPTC for ex : # convert foo.jpg foo.png # convert foo.png foo2.jpg open foo.jpg, foo.png and foo2.jpg in showfoto and look like Exif and iptc still here ! This method to embeded metadata in PNG come from ImageMagick. I have personally backported this code in digiKam core ! I'm use PNG everywhere and my pictures are always taken in RAW. I convert all RAW file to PNG when i work. I never use TIFF because ... while TIFF keeps it intact. False... under Linux ! Of course, TIFF norm ask than tiff file format must preserve metadata, but this is not the reality. All open source software (UFRAW, ImageMagick, Gimp, etc) use Libtiff to handle tiff files. With this library, XMP and IPTC can be preserved, but never Exif and Makernote, duing a big limitation in libtiff implementation. In fact try this second ex. : # convert foo.jpg foo.tiff # convert foo.tiff foo4.jpg ... and look like Exif and makernote have disappear ! It's a shame for a photograph !!! This is why i _NEVER_ use TIFF file format. As for which to use, it really depends. I tend to use TIFF because it can support other color spaces and greater bit depth (as I shoot RAW). PNG support 16 bits color depth and ICC color profiles. You can work on Adobe RGB and Wide Gamut RGB to convert you RAW pictures as well This situation around TIFF will change when Exiv2 will support Tiff file acces in writting mode. Like this we will delegate to Exiv2 all metadata management for TIFF file, and Exif/Makernote will be preserved. But at this moment, PNG is the best solution to work with digiKam under Linux. Gilles Caulier _______________________________________________ Digikam-users mailing list [hidden email] https://mail.kde.org/mailman/listinfo/digikam-users |
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