[Digikam-devel] digikam PNG workflow...

[Caulier Gilles]

Le Lundi 23 Janvier 2006 23:18, Thorsten Schnebeck a écrit :
> > Well RAW file formats are the big bazard. there is nothing homogenous and
> > anyone includes metadata, anyone no. For more information about RAW files
> > problems, take a look in openraw web site :
> >
> > http://www.openraw.org/
> >
> > In all cases, PNG is better than RAW, because :
> >
> > - It's a GPL-iszed standard... better than DNG that there is no lib to
> > manage it. It's an non-standard file format provide by a commercial
> > compagny : Adobe (tm)
>
> DNG is tiff, libtiff supports DNG although I have not found a code sample
> showing how to create a DNG file cause interaction with dcraw is for sure
> necessary. I know there are programs that create DNG files with libtiff and 
> dcraw.

Yes, i know, but you forget than DNG need to have a lib about a new metadata 
format from adobe (tm) : RDF. This is not EXIF and IPTC. Actually, only Exif 
metadata are supported by digiKam.

> While its true that DNG is not an etasblished format you can make a step
> back and look at others Adobe open formats like PostScript, TIFF or PDF.
> All of these file formats are well known industry standards. Adaption of
> DNG just starts (Samsung, Hasselblad) and got some positive comments also
> from the openraw campaign.
> If you want some samples here is a complete processed toolchain:
> ftp://ftp.graphicsmagick.org/pub/outgoing/tiff-exif-dng/

yes, but i'm not agree with openraw goal. DNG isn't the unique solution to 
make a digital negative file format. PNG can do it easily....

>
> > - It's can be displayed without problem by all web/file managers.
> > - It's can be decoded more speedly than RAW files (:=))).
> > - It's a RW file format, not RAW files.
> > - It's can be compressed like TIFF with a better ratio, and _LOSSLESS_ !
> > - It's can be read on all computers. There are no PNG patents...
> >
> > Using libPNG is easy and ready to use now. I have just need to add any
> > lines of code in png image loader to backup/extract JPEG metadata (:=)))
>
> All true, but can digiKam establish a PNG metadata standard? 

Digikam no, but PNG team yes. If tere is any PNG team member in this room...

> If I create a 
> PNG file with digiKam with an e.g. embedded ICC profile other programs do
> not understand, it is not that good. 

No. there is already a standard PNG tag for ICC profile ! This is not a 
problem.

With libPNG, you can create a new tag without compatibilty problem (this is 
the power of PNG) Using this way, you don't break compatibilty.

If you want, i can create a PNG file with an EXIF tag to test (:=)))


> If we use PNG simply as an extendable 
> storage container we lose compatibility.

NO ! Read libpng documentation before !

>
> As a user I would vote for a temporary PNG solution and switch over to DNG
> when the libs are ready and handy.

I a new DNG loader in the future to Digikam::DImg API, when a GPL lib will be 
availalble, or if a contributor want create this loader from strach using 
only DNG spec. personnally, i have no time to do it...

Gilles