[poppler] Fwd: Re: PDF rendering with Poppler

Brad Hards bradh at frogmouth.net
Fri Dec 23 01:55:05 PST 2005

Lars Knoll blogged about some problems rendering the PDF generated by Qt4.1. 
Basically, they tested the PDF that they generate with xpdf/poppler, 
ghostscript and acrobat viewer. The tests were done with the "as installed" 
versions of those tools, so they may have already been fixed, especially with 
our recent merge of the latest xpdf code. The current answer to those 
problems is not to generate problematic PDF, however the long term answer is 
to fix our handling.

The specific problems that Lars identified are:
* regular masked images (image dicts with a /Mask entry)
* softmasks on Images (image dicts with a /SMask entry)
* constant alpha in the graphics state
* softmasks in the graphics state
* ShadingType 4 shading dictionaries
* shading dictionaries as softmasks in the graphics state

Most of the above are needed to implement transparency support as we have it
in Arthur (Qt's painting abstraction).

As shipped in Qt4.1, the PDF generator does not do softmask in the graphics 
state and type 4 shading. That allows ghostscript to work.  Bug reports / 
test cases are promised post-holidays.

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