[digiKam-users] Thumbnails are in Progessive Graphics File (PGF)

[Gilles Caulier]

Le ven. 31 janv. 2020 à 03:15, Striper <barry at bytescience.com> a écrit :

> Although I understand your arguments and reasoning, I do not fully agree
> with
> you. PGF may be the best technical solution for storing thumbnails (or any
> graphic image for that matter), it's definitely not the best solution from
> an interoperability standpoint. The simple fact that Google expands its
> search results for "PGF" with hits on "PDF", means that this format is not
> widely used nor supported. Except for the C++ implementation on SourceForge
> (libPGF), there is not a single library or utility to be found that can
> decode or encode this format. In other words, unless you are developing in
> C++, it's useless.
>
> There are countless examples of inferior technology that became the
> standard
> over a superior technology (Betamax vs VHS is a classic). For techies like
> myself, that hurts, but it is a fact of life that we have to live with.
>
> The great thing about open source is that everybody can use it the way they
> want to. Digikam is a great product and I love it, but using this kind of
> exotic formats hampers the "openness", in my opinion. Would anybody really
> notice the difference in performance or quality when the thumbnails are
> stored as JPG or PNG? Would a few extra bytes really matter when we are
> already storing gigabytes of RAW and JPG images?
>
> PGF is so far interresting in regard of thumbnails storage in the
database. It use wavelets algorithm which compress better than JPG and of
course all other image format (PNG, TIFF RAW)

Algorithm is also very optimized : faster and quality. Using JPEG for
thumbnails storage is not the best choice, even is compressing time is
mostly the same.

Writing a small CLI tool to extract PGF from database and export to JPEG
already exists in digiKam unit tests. Remember that libpgf source code is
embedded in digiKam core.

So to export this code and make a extra project is possible for this
function, if somebody is ready to help.

Best

Gilles Caulier
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