[poppler] Annotation appearance streams

[Carlos Garcia Campos]

El lun, 01-06-2009 a las 14:45 +0200, Carlos Garcia Campos escribió:
> Hi all, 
> 
> I'm working on adding support for creating new annotations that can be
> added to any document. The idea is just adding new constructors to the
> existing Annot objects that don't require an annot dict, and setters for
> the annots attributes. I don't know what to do with appearance streams,
> though. Ideally, appearance streams should be built by the poppler core
> to avoid duplicated code in the frontends. But appearance streams of
> annotations are actually form XObjects, they are not usually a bitmap,
> but a sequence of instructions to draw the annotations. For example:
> 
> q
> g 0.5
> G 0.75
> i 0
> M 4
> m 2.0938 18.2158
> l 2.0938 0.5
> l 12.0962 0.5
> l 17.1577 5.5615
> l 17.1577 18.2158
> l 2.0938 18.2158
> h
> B
> rg 1 1 0
> G 0
> m 0.5 19.8096
> l 0.5 2.0938
> l 10.5024 2.0938
> l 15.564 7.1553
> l 15.564 19.8096
> l 0.5 19.8096
> h
> B
> m 10.46 2.1338
> l 10.46 7.167
> l 15.5225 7.208
> S
> m 4.0537 15.9824
> l 12.0537 15.9824
> S
> m 4.0537 12.9824
> l 12.0537 12.9824
> S
> m 4.0537 9.9824
> l 8.9912 9.9824
> S
> Q
> 
> This is the appearance stream used by acroread to render Note icons used
> in Text annotations. In the case of Text annotations we should provide
> predefined appearance streams for the well-known icons:
> 
>  - Comment 
>  - Key
>  - Note
>  - Help
>  - NewParagraph
>  - Paragraph
>  - Insert
> 
> but for the other annots we need to figure out a way to set an
> appearance stream. I'm afraid it's not going to be possible to build the
> streams in the core, so the api might be just Annot::setAP (Stream
> *str); and build the appearance streams in the frontends or even in the
> viewers. 

well, there's another possibility: don't provide any appearance stream
at all, like this PDF:

http://www.pdfill.com/example/pdf_commenting_new.pdf

The problem is that it doesn't work with current poppler, because we are
only drawing annotations that have an AP (which is something we should
fix anyway)

> any other idea? am I missing something? any artist willing to write
> icons for Text annotations? :-P
> 
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-- 
Carlos Garcia Campos
   elkalmail at yahoo.es
   carlosgc at gnome.org
   http://carlosgc.linups.org
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x523E6462
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