[Bf-committers] GPencil I/O Project: Request to integrate libharu lib to export PDF format

[Brecht Van Lommel]

I'm not sure there exists a simple utility to convert SVG to PDF that we
could include, if we want to go that way?

Inkscape uses Cairo for PDF writing, that could be a more actively
maintained alternative.
https://www.cairographics.org/

It has also been proposed to be added to handle Wayland window decorations
in D7989, so it would let us solve both problems with one library.


On Wed, Dec 9, 2020 at 11:46 AM Antonio Vazquez via Bf-committers <
bf-committers at blender.org> wrote:

> There are several reasons why I decided to use libharu.
>
> * The PDF format is very stable and does not change substantially, so we
> are not at great risk due to format changes.
> * I already know that this library is not maintained, but since the PDF
> format does not change, it does not require much maintenance.
> * This library is widely used in other software to generate PDF, so it is
> well proven.
>
> Regarding the bugs you comment, I have seen that several have a patch to
> solve them, but in any case, the use I make of the library does not include
> using images, only a very simple use. I do not expect, in the short or
> medium term, to use anything related to appending images, so these bugs do
> not affect us at all. Attaching images to a PDF does not make much sense in
> our case.
>
> Including a converter from SVG could work, but the problem is that in PDF
> we can generate a document with several pages and in SVG I have not seen
> that this is supported. Imagine that we want to generate a storyboard with
> 100 frames ... we would need to export 100 SVG and join them later ... now
> that is very simple. We would also have to assess the speed of the
> conversion, since now it is all C / C ++ and it is very fast.
>
> The other option I have been considering is to fork libharu and create a
> tiny version with the functions we need and remove any appended image
> support.
>
> Antonio
>
> El mié, 9 dic 2020 a las 0:46, Campbell Barton via Bf-committers (<
> bf-committers at blender.org>) escribió:
>
> > Hi Antonion,
> >
> > From what I can tell libharu hasn't been very active since 2013, their
> > site states they're looking for a new maintainer.
> > Would we become the defacto maintainers of this library?
> >
> > I checked their issue tracker, while many reports are support requests
> > and build issues, there are some more serious looking issues too, eg:
> >
> > https://github.com/libharu/libharu/issues/73
> > https://github.com/libharu/libharu/issues/71
> > https://github.com/libharu/libharu/issues/63
> >
> > Is there a significant advantage in integrating a library compared
> > with bundling a utility that converts SVG to PDF?
> > In this case it could be an optional dependency, or we bundle the
> > conversion tool in official releases so PDF support is still
> > integrated from a user perspective.
> >
> > On Wed, Dec 9, 2020 at 6:31 AM Antonio Vazquez via Bf-committers
> > <bf-committers at blender.org> wrote:
> > >
> > > Hi All,
> > >
> > >
> > >
> > > As some of you may already know, for version 2.92 we want to focus on
> the
> > > Import and Export processes of Grease Pencil (T83190).
> > >
> > >
> > >
> > > Currently, the grease pencil is in some way an "island" in the studios
> > > pipeline and we need to add tools to integrate it. Part of these
> > > integration processes were the work we did to make image traces (2.91)
> > and
> > > shortly, video traces (2.92).
> > >
> > >
> > >
> > > During the contacts that the members of grease pencil team usually have
> > > with 2D studios, they have detected that some commercial software very
> > > important in the studios pipeline does not support the import of SVG,
> but
> > > of PDF. In addition, the PDF format allows working in many softwares
> and
> > is
> > > very useful for generating storyboards and work in comics.
> > >
> > >
> > >
> > > Past weeks, I have been working on a new I/O module for grease pencil
> in
> > C
> > > ++ and I already have the SVG Importer (T79875) and the SVG Exporter
> > > (T83191) and PDF Exporter (T83192) working. All work has been done on a
> > > private branch on my PC.
> > >
> > >
> > >
> > > You can see a PDF exporter video here: https://youtu.be/BMm0KeMJsI4
> > >
> > >
> > >
> > > To export to PDF I have used an open source library (libharu
> > > http://libharu.org/) and would need to integrate that library into
> > Blender.
> > > This library is very simple (<1.6 MB on Windows) and allows export to
> PDF
> > > easily.
> > >
> > >
> > >
> > > Finally, exporting to PDF opens up a world of possibilities and
> > especially
> > > when the new LineArt module will be integrated into Blender.
> > >
> > >
> > >
> > > If we agree to integrate libharu, I can prepare the patch for review
> the
> > > I/O code I did.
> > >
> > >
> > >
> > > I would like to hear your opinions.
> > >
> > >
> > >
> > > Best Regards,
> > >
> > > Antonio Vázquez
> > >
> > > Grease Pencil Team
> > > _______________________________________________
> > > Bf-committers mailing list
> > > Bf-committers at blender.org
> > > https://lists.blender.org/mailman/listinfo/bf-committers
> >
> >
> >
> > --
> > - Campbell
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