Feathering from Word PDFs just grey

[MickRose]

This is a problem with the release version and the beta version. When I open a PDF supplied by a customer which contains feathered images the feathering part comes out as a grey image rather than coloured. If I flatten the supplied PDF by printing to PDF/A-1b:2005 (CMYK) the feathering stays coloured when opened in Publisher. It looks like Publisher is struggling to handle the layers.

[MickRose]

For what it's worth Quark is even worse with this file. The displayed image and the exported PDF also display the feathering as grey.

[Gabe]

Hi @MickRose,

Can you use this link to upload the PDF please? https://www.dropbox.com/request/p06S0D9ou8nX1GNEU1gx

[MickRose]

Hi Gabe - I've uploaded some files. It looks like it's when I use Word to "save as PDF" that the problem happens. If I print to PDF from Word the feathering is okay in AfPub

[Gabe]

Thanks. There is no feathering in the PDF you've attached, so no feathering for us to import. 

[MickRose]

Sorry - maybe I sent the wrong files. I've just sent 2 new files. One created by saving the Word file as PDF. The other by printing to PDF. Both are feathered on screen. The feather on the one created by saving Word file as PDF has a greyish colour when opened in Publisher.

 

[Gabe]

It looks like a pre-multiplying issue. What word version are you using? We can't replicate the issue here if we export a fresh version from Word 365. 

FWIF Adobe seems to flag it too:

 

[MickRose]

I use Word 2010. My customer uses Word 2019.

[Gabe]

It looks like Word 2010 uses a premultiplied alpha, whereas the 365 one uses a "straight" alpha. Nothing wrong with either, but the pre-multiplied one needs more attention and a bit more work. You would need to divide it by alpha (Filters > Colours > Divide by Alpha). 

[MickRose]

Hi Gabe - Thanks for that tip. It sort of works but I have apply that filter quite a few times to get the feathering as it should be. It does have the advantage of not segmenting the image (this seems to happen if I print the Word file to a PDF file).

[MickRose]

Hi Gabe - I've found that if I click on the problematic image in Acrobat Pro, Edit Image in Photoshop, convert to CMYK and save the PDF - the image opens correctly in AfPub.

[Gabe]

I suspect that changes the alpha from pre-multiplied to straight. 

[MickRose]

Yes, I think that's right. To be honest I'd never heard of these alpha channnel options before but it seems a badly implemented pre-multiplied alpha channel can give a grey halo around the object. Saving a CMYK converted Photoshop image must convert it to straight alpha. So I'd guess the problem is in how Word creates its image effects. The learning curve goes on!