On Thu, Dec 11, 2014 at 7:35 AM, [email protected] <
[email protected]> wrote:

>
>
> On Thu, Dec 11, 2014 at 5:12 AM, Daniel Sim <[email protected]
> > wrote:
>
>> >
>> > I don't think you need extensions to PDF, but of course I don't know
>> your
>> > goals. I would imagine that
>> > using the /AP section of an ink annotation you can do whatever you
>> want, but
>>
>> From a quick reading of the PDF spec 1.7 it seems the /AP section just
>> contains the same entries as in a regular Ink Annot. Not quite what I
>> wanted -- I wanted to add a *new* entry called InkWidths, an array of
>> array of reals, whose lengths matches that of InkList, that specifies
>> how thick the ink is at each segment.
>>
>
> mmm. /AP stands for Appearance Stream, AFAIK, you can put any DRAWING
> command there...which will be similar to a sequence of cairo commands,
> including commands to change the width of the line.
>
>
Actually, here is a pdf that "seems" to implement variable width for ink
annotations. Whatever commands there, you could mimic them in order to get
your desired width change according with the pressure.

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




>
>> In Xournal, you get very nice inks using this feature and a
>> pressure-sensitive tablet! But yea, it would't make sense to do this
>> as a start.
>>
>> Do you know, by any chance, how PDF readers are supposed to handle
>> unknown Dict entries?
>>
> They don't.
>
>
>>
>> > I haven't try it though. In any case, iI think it would be
>> > best to first implement things that conform to the PDF spec. If you
>> still
>> > want to do extensions, I guess they can be saved as metadata together
>> with
>> > the file (this of course may cause problems when copying the file.. or
>> send
>> > it) or just doing a sort of PDF + json or whatever you like (but in two
>> > files could be simpler for evince)
>>
>
>
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