[pdftex] bug with included transparent graphics

Jim Diamond Jim.Diamond at acadiau.ca
Mon Dec 31 19:42:13 CET 2007

On Mon, Dec 31, 2007 at 16:27 (+0100), Martin Schröder wrote:

> 2007/12/31, James Quirk <jjq at hmx.galcit.caltech.edu>:
>> The posting has elicited the following response
>> which is along the lines you were thinking:

>> ----------- http://www.adobeforums.com/webx/.3c05ae39/0
>> It's not that the PDF is erroneous - it's a perfectly valid PDF. However,
>> it isn't taking into account the fact that when transparency is present,
>> Acrobat (as per the PDF Reference) uses a different "path" to rendering
>> that involves an "transparency blending space". By default, that space is
>> DeviceCMYK and thus your RGB colors are being converted to CMYK when
>> rendered.

>> If pdfTeX were to add a /Group dictionary to any page containing
>> transparency and specify in there to use /DeviceRGB instead as the
>> blending space - your colors wouldn't shift.

> Yes,
> Leonard already told me the same.

> I'll fix this next year. :-)

Geez, we have to wait that long??  ;-)

But here's two serious questions:

(1) Does the fact that kpdf and xpdf (at least on Linux) render this
    file as expected indicate that they both have bugs?

(2) Some people (windows?  mac?) said it works correctly for them with
    Adobe reader.  What's up with that?

Cheers.  And thanks to everyone who has been looking into this.

Best wishes for 2008.


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