[poppler] Problem understanding Optional Content

[Leonard Rosenthol]

On Nov 6, 2007, at 9:41 PM, Brad Hards wrote:
>> Then as you render, you need to check each piece of content to see if
>> it lies inside of an OCG, and whether that OCG is "On" or "Off" at
>> this time.
> Yep. What I don't see is "how do I tell if this item is part of an  
> OCG or not"
> for most of the items.

	Look in the content stream for /OC MC0 /BMC.

	You need to track marked content operators and see what type of MC's  
they are (since MC is used for a variety of things, of which OC is  
just one).  Remember that it's a stack, since you can have multiple  
OCs on a single piece of content.


>> If you need any more samples or help - just holler!   It would be
>> great to see a Poppler client support OCGs...
> Samples are always good :-) In particular, something showing OCMD, and
> something showing VEs would be very nice. Even nicer if we can  
> redistribute
> them in our test cases.
>

	Enclosed are two good OCMD test files - one with a simple "flat" set  
and one that also demonstrates "hierarchical" grouping.   You are  
welcome to include them in your test cases.

	I'll try to dig up an VE sample for you...
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Leonard