[pdftex] bug with included transparent graphics

Paweł Jackowski P.Jackowski at gust.org.pl
Mon Dec 31 14:20:59 CET 2007

Martin Schröder pisze:
> 2007/12/30, James Quirk <jjq at hmx.galcit.caltech.edu>:
>> After looking inside the PDF I generate at my end (I'm using pdftex
>> 1.40.3-2.2) it looks like the /SMask for the png image is affecting the
>> whole page. For instance, one can comment out "/Im1 Do" from the page
>> stream, to suppress the png image, and the color for page 2 is still
>> affected. On the other hand, if the /SMask is commented out of
>> the png's /XObject then the png is drawn without transparency (the cutout
>> appears as a red square) and the color for page 2 is correct.
>> I havn't yet fully digested the PDF Reference to know whether
>> AR is at fault or pdftex is generating erroneous PDF.
>> Martin do you have a feel for which it is?
> No. But I wouldn't be surprised if AR needs the same kind of magic as
> with page groups (i.e. an image with a /Group key works only on a Page
> with a /Group key), i.e. an image with /SMask needs some magic in the
> Page object to work correctly. Or it's simply a bug in AR8 at Linux.
> Can anybody please confirm the behaviour on Windows or MacOS?

On Acrobat 8.1 prof (under Vista) and Reader 7.0 (XP) I do see a 
difference in colour. It looks like Acrobat simulation of the output 
gamut. For some reasons, Acrobat recognizes page 2 as the output to be 
printed not displayed, and simulates (implicitly) a color offset on the 
output device. The same happens once you turn on 'Output preview' option 
(prof only) on the first page; all the colors looks somewhat different 
with this turned on/off. Have screenshots if one interested.

Pawe/l Jackowski
P.Jackowski at gust.org.pl

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