Andreas Vox wrote:
> Hi Craig,
>
> as I read the PDF reference, that sequence is legal. The restriction  
> on BMF/EMF is just not to break up any *graphic objects*, but paired  
> graphic state operators don't matter. This makes sense, since BMF/EMF  
> is supposed to be a very general markup facility which should also  
> allow to mark eg. "setup page" or "page trailer" sequences. The  
> restrictions on BT/ET are neccessarily much stronger. Also specific  
> variants of BMF/EMF pairs might need further restrictions, but that's  
> application dependent.
>
>   

I expect you're right, as I couldn't find anything to the contrary and 
Adobe's own usage fits with that. I guess that means there's no neat way 
to provide a generalised tree representation of the content stream.

I might just ditch the idea and leave it to users to implement what they 
need based directly on Dom's PdfContentsTokeniser. I was hoping to 
provide something higher level and suitable for use with generalised 
algorithms (for example, scanning a contents stream and converting all 
colours to RGB) so that users didn't have to write the guts of the 
process themselves for each operation... but I'm not sure I can come up 
with something more useful than a flat list unless there's a strong 
guarantee of nesting rules for large sets of operators.

Thanks for looking into this Andreas.

--
Craig Ringer

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