[poppler] Black boxes & Poppler

[Thomas Freitag]

Am 14.02.2012 23:17, schrieb Albert Astals Cid:
> El Dimarts, 14 de febrer de 2012, a les 20:35:29, Thomas Freitag va escriure:
>> Hi Albert!
>>
>> Am 14.02.2012 18:07, schrieb Ralph Gootee:
>>> Hi Thomas!
>>>
>>> Thanks for the help!
>>>
>>> Steps to reproduce
>>>
>>> 1) split the pdf with pdfseparate
>>> 2) use pdftopdf to convert the output to png
>>>
>>> Also, the PDF errors out acrobat after separation.  It's a little
>>> confusing but there's already black boxes in the pdf (from redaction)
>>> the black boxes will show up in the middle after pdftoppm.
>>>
>>> We're really really happy with poppler, thanks for helping to make such
>>> an awesome lib!
>> We have two problems with it, one is a general problem coming from the
>> merge:
>>
>> a) xRef->getNumObjects() will no more work with the changes from our/my
>> merge in PDFDoc::writePageObjects, 'cause last is not set here. We need
>> to use xRef->getSize().
> We use getNumObjects in a lot of other places, aren't those affected too?
> Shouldn't we just revert getNumObjects to do what it did? i.e. kill the last
> variable and just return size? What's the benefit of this last variable?
in the other places getNumOnjects() will work: last is filled during 
creating the XRef table in readXRefTable, and has the number of the last 
valid xref, where as size is the number of allocated xrefs.
This optimization is coming from the merge. The problem in 
writePageObjects is the the xref table wasn't read but is indirect 
created, therefore we must use size there, also because xrefs are here 
not created necessary in ascending order.
In short terms: in all other cases it is okay to use getNumOnjects.

Thomas
>
> Albert
>
>> b) CCITTFaxStream and DCTStream are enherited by FlateStream, and the
>> FlateStream::reset "eats" the first two bytes. Therefore a call of
>> unfilteredReset will not work in pdfseparate. As far as I can see,
>> unfilteredReset is just called by PDFDoc::writeRawStream (or in
>> Stream.cc itself), therefore I think my changes in the attached patch
>> are safe.
>>
>> a) is the reason why I send this patch immediately and do not wait until
>> the weekend: pdfseparate and pdfunite will no more work on the HEAD
>> revision.
>>
>> @Ralph: You need to check out the head revision and apply this patch, if
>> You want to test it immediately.
>>
>> Cheers,
>> Thomas
>>
>>> Cheers,
>>> Ralph G.
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