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normanius
Participating Frequently
August 9, 2019
Answered

Create portable PDFs with illustrator that correctly handle transparency flattening

  • August 9, 2019
  • 2 replies
  • 1767 views

Dear all

Background:

I'm working with PDFs created by some toolbox - in my case it's python and matplotlib. My graphs contain circular and cross-shaped markers that are outlined by an edge. These markers I will use in this question to illustrate my problem(s). Both fillings and edges of the markers are painted with alpha=0.7.

My workflow is very common in an academic context:

  1. Create scientific graphs with some data processing tool, export graphs to PDF
  2. Adjust graphs for publication (fonts, spaces, colors, legends, etc...)
  3. Insert the vector graphic in MS Word (some journals only accept .docx files!)

My system: Adobe Illustrator 23.0.4, on MacOS 10.14.5, all screenshots were taken on the same screen.

Problem description

MacOS' default PDF viewer displays the markers as shown in screenshot 1.

If I import this PDF directly into Powerpoint, the markers are shown roughly the same (screenshot 2).

Screenshot 1: Apples' PDF Preview, left

Screenshot 2: MS Powerpoint, right

Now, if I open the PDF in Adobe Illustrator (version 23.0.4), a first thing that I notice is that the marker edges of the plots are shown with a white frame around it (see screenshot 3). It appears that the filling and the outline of the markers are represented by two different elements. Changing the way how the marker is created is out of debate in this context.

Screenshot 3: Adobe Illustrator 23.0.4, left

Screenshot 4: Adobe Illustrator, right (detailed view showing the elements of the marker)

Look at screenshot 5 and note that the outline (left) throws a white border on the filling (right). Interestingly, this white outline border disappears if an edge is added to the filling, even if the border is minuscule (screenshot 6)!

Screenshot 5: Adobe Illustrator (detailed, showing the white frame, the filling object is colored differently to better see the effect)

Screenshot 6: Adobe Illustrator (detailed, white frame around outline not present if filling has an edge with non-zero width)

If I save the project in Illustrator as PDF, the PDF shown in MacOS Preview looks still okay. But Powerpoint (actually: any Microsoft Office tool) cannot render the output correctly. See screenshots 7 and 8.

Screenshot 7: MacOS Preview, left - PDF created by Illustrator (PDF Preset: Illustrator default, standard: None, compatibility: Acrobat 6 (PDF 1.5))

Screenshot 8: MS Powerpoint, right - same PDF as in screenshot 7, rendering of PDF is completely messed up in MS Office software

I finally observed that the choice of PDF standard is key to create a PDF compatible with Microsoft tools (actually, anything higher than compatibility "Acrobat 4 (PDF 1.3)" does not work with MS Office tools). Standards PDF/X-1a:2001, PDF/X-1a:2002, PDF/X-3:2002 and PDF/X-3:2005 work, but not PDF/X-3:2010. However, working with Acrobat 4 compatibility breaks the appearance of the markers , see screenshot 9, 10 and 11. While one probably can live with the difference in 9 and 10, screenshot 11 is a show stopper.

Screenshot 9: Apples' PDF Preview, left (PDF created by Illustrator, with compatibility for Acrobat 4)

Screenshot 10: MS Powerpoint, right (same PDF as in screenshot 9)

Screenshot 11: Apples' PDF Preview, left (same PDF as in screenshot 11, different

I believe this is related to transparency flattening, but I was not able to figure out the proper settings to recover the input PDF (screenshot 1).

I also tested to export to EPS - but the problem are the same as with PDF.

Questions

I know that I'm addressing several, probably unrelated problems:

  1. What is the matter with PDF standards? Why does Powerpoint (actually any Microsoft Office software) fail to render newer PDF standards? The compatible standards are 15 years old and more!? How to work around these appearance problems?
  2. How to handle transparency flattening properly for Acrobat 4 compatible PDFs, which I require for use with Microsoft Office (at least on MacOS - haven't checked the problem on other operating systems)
  3. Why doesn't Illustrator render the original PDF just like other viewers do (MacOS Preview, Microsoft Powerpoint)? Compare screenshot 1 vs. 3. Fore example: why is there the white border around the outline object in Illustrator? I upgraded from Illustrator 19.x to 23.x, but the problem persists. So I guess it's standard behavior, rather than a bug.

Because I bumped into these problems already several times, I decided to spend a bit of effort to describe all these issues. For me, it is not an option, to always adjust the graphs until the publishing tools can handle the PDF. (There are too many tools, and adjusting plotting functions typically is a nightmare. Therefore I'm wondering what the best practices are to handle these portability problems!

I'd be massively grateful to receive some help here!

This topic has been closed for replies.
Correct answer Ton Frederiks

The objects where created as groups, made from 2 identical shapes

One has a stroke and one has a fill and both have 70% opacity.

Normally this would make a visible darker area, as shown in Apple Preview.

But because the group has an Opacitiy attribute “Knockout Group”, it does not show the darker overlapping area in Illustrator and Acrobat.

If you want it to show as in Apple Preview, with the darker lines, you can Select All and choose Object > Ungroup, that will get rid of the Knockout groups and the “white” lines.

2 replies

Ton Frederiks
Community Expert
Ton FrederiksCommunity ExpertCorrect answer
Community Expert
August 9, 2019

The objects where created as groups, made from 2 identical shapes

One has a stroke and one has a fill and both have 70% opacity.

Normally this would make a visible darker area, as shown in Apple Preview.

But because the group has an Opacitiy attribute “Knockout Group”, it does not show the darker overlapping area in Illustrator and Acrobat.

If you want it to show as in Apple Preview, with the darker lines, you can Select All and choose Object > Ungroup, that will get rid of the Knockout groups and the “white” lines.

    T
    Test Screen Name
    Legend
    August 10, 2019

    No workflow should include “edit a PDF in Illustrator” unless the PDF was made in a Illustrator. AI is NOT A GENERAL PDF EDITOR. No matter how much people want it to be. And it will not be. 

    No software exists to reliably perform your step 2.  Acrobat certainly can’t be used to fix up work to press requirements.

    Monika Gause
    Community Expert
    Monika GauseCommunity Expert
    Community Expert
    August 12, 2019

    Thanks for the clear announcement. People should know this!

    To complete your answer, what would you suggest me to do? Because scientific plotting tools are limited or difficult to use, I need a manual editing step to comply with the requirements imposed by scientific journals.

    Would a different output format in step 1) of my workflow be of any help. For example any of .ps, .eps and .svg?

    And just out of curiosity: How comes AI is not a general PDF editor? I mean Adobe invented the format and owned it until 2008? And even if it's not Adobe, why should it be impossible to develop a tool to reliably edit PDFs?


    normanius  schrieb

    And just out of curiosity: How comes AI is not a general PDF editor? I mean Adobe invented the format and owned it until 2008? And even if it's not Adobe, why should it be impossible to develop a tool to reliably edit PDFs?

    PDF was never even meant to be edited. It started off as a presentation format.

    And then: a PDF can be generated by so many apps and might contain so many different kinds of content that Illustrator doesn't even know off. In order to be able to display the content exactly the same on all kinds of systems and devices, the content has to be set up in a way that makes it difficult to edit. Even if it has beencreated in Illustrator (but saved without "Illustrator editing capability") it will not be fully editable anymore when opening the PDF in Illustrator. And this is by design.

    But also: PDF is standardized, so Adobe gave away a lot of control over the file format.

      Ton Frederiks
      Community Expert
      Ton FrederiksCommunity Expert
      Community Expert
      August 9, 2019

      Can you share the PDF that you show in your Screnshot 1?

      N
      normaniusAuthor
      Participating Frequently
      August 9, 2019

      Find the file here. (Not a permalink, let me know if there's a better way how to share PDFs in this forum.)

      Ton Frederiks
      Community Expert
      Ton FrederiksCommunity Expert
      Community Expert
      August 9, 2019

      Thanks, I'll have a look at it.

      First thing I noticed, the GPU Preview causes those white lines.

      Try Cmd E to switch to CPU Preview.

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