[poppler] thumbnails

[Shawn Rutledge]

On Tue, May 19, 2009 at 2:52 PM, Albert Astals Cid <aacid at kde.org> wrote:
> A Dimarts, 19 de maig de 2009, Shawn Rutledge va escriure:
>> Is there support for reading thumbnails that are embedded in a PDF
>> file?
>
> Poppler core has it
>
>> I get the impression that most PDF viewers aren't using those.
>
> Because are of hardcoded and makes no sense in a world were most PDF viewers
> let you resize randomly the thumbnail bar. Also i'm not sure if the number of
> PDF files with embedded thumbnails is "high".

Rendering each page is slow that way though.

Acrobat 7 used the thumbnails nicely: when opening up a PDF that has
them, they display very quickly, and it was possible to drag pages
around to re-order them.  Acrobat 9 has the resizable thumbnails, so
now it's very slow, and stupidly it re-renders them every time they
are scrolled into view or re-ordered, so this kind of "slide-sorter"
method of putting pages in order is now impractical.  (Of course they
should at least cache them in memory, and should use multiple cores to
speed it up, but they don't.)

I also was wondering if today's GPUs could render PDFs somehow, fast
enough to get all the thumbnails cached at a rate of 100 pages per
second or so, but that's another topic.  Maybe somebody needs to start
a CUDA poppler implementation?  :-)  (not that I have any experience
with that sort of thing, it's just a brainstorm)

>> And I don't really see how to get them using the Qt4 bindings, at
>> least.
>
> Right, the Qt4 bindings don't expose thumbnail reading, if you'd like to have
> them, do you think you can contribute a patch?

Probably I could, I'm familiar enough with Qt although haven't looked
at the implementation of those bindings yet.  Can you give a general
outline how to get the thumbnails using core?