[pdftex] bug with included transparent graphics

[James Quirk]

On Mon, 31 Dec 2007, Martin Schröder wrote:

> 2007/12/31, James Quirk <jjq at hmx.galcit.caltech.edu>:
> > the page colours and so it looks like it is a Linux-specific bug. This is
> > unfortunate as the pre-release program for Linux AR8.1.2 has just closed
> > and so it might be some time before a bug fix can make it to a public AR
> > release.
> 
> I see that you have already forwarded that to Adobe
> (http://www.adobeforums.com/webx/.3c05ae39); thanks.
Martin,

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.

Leonard Rosenthol 


> 
> Have a happy new year
>    Martin
And you too.

James



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