Ubuntu – Flattening PDF transparency

inkscapepdfprintingvector-drawings

I have a PDF, made with Inkscape, that uses transparent colors. This image shall be used in a LaTeX document.

While preserving the transparency is nice for editing, it can be a problem for printing. Printing usually involves PDF to PS conversion. Since Postscript does not support transparency, this requires either

flatting, i.e. creating a vector graphic that works without transparency

rastering, i.e. rendering a bitmap image.

When a PDF document containing such a figure is printed (or converted to PS) using Evince (or Cairo or Ghostscript), the whole page gets rendered as a bitmap, rendering fonts ugly (different from other pages). (Adobe Acrobat handles such PDFs well.)

Unfortunately, converting the PDF figures to EPS (before including them with LaTeX) doesn't help much, because both pdftops and pdf2ps (again, Cairo or Ghostscript) rasterize the image, i.e. render a bitmap (saved as EPS). (This is slightly better, because it doesn't affect the whole page, but I'd still prefer a vector graphics.)

How can I flatten transparency with Inkscape or other software on Linux?

Best Answer

One way around bad rasterization is to manually convert your PDF document to postscript because when you invoke CUPS through evince or whatever gui, it will be converted anyways.

You can try pdftops -r 1200 document.pdf to increase the resolution from the low default of 300, and then print the resulting postscript. However, with the printers at work this did not yield a significant improvement. Regular text on pages with and without transparent images still looked different -- blurry vs. clear.

So I ended up using Acrobat Professional (on a windows machine) to flatten the transparent images used in my latex document, which gave optimal results. Check that Transparency Flattener Preset is at [High Resolution] in the advanced print setup. My colleague mentioned that one could perhaps FTP a pdf file directly to a modern laserjet network printer, bypassing the postscript conversion. I have not tried this.

Would be great to have linux-only solution to this issue.

Related Solutions

Ubuntu – Batch convert ai files to pdf / png etc

You can use GhostScript for batch output .ai to various formats, i.e. transparent PNG:

gs -dNOPAUSE -dBATCH -sDEVICE=pngalpha -r300 -sOutputFile=out.png in.ai

Where -r300 is dpi resolution.

For available devices with which you can convert .ai format, reference documentation.

Ubuntu – How to edit a picture into an existing PDF file

My recommendation is Xournal and its actively developed fork, Xournal++. Here are the instructions.

Install (for Xournal):

sudo apt-get install xournal

For Xournal++ you can use either the stable PPA,

sudo add-apt-repository ppa:apandada1/xournalpp-stable
sudo apt update
sudo apt install xournalpp

or the flatpak,

flatpak install flathub com.github.xournalpp.xournalpp

Run xournal or xournal++, click File>Annotate PDF, choose your PDF file.

Now, go to where you need to add your signature and click Tools>Image (or the "Image" toolbar icon), then click where you want to add the image. An image selection dialog appears, select your image.

Xournal's insert image is a great addition but not polished. As soon as you add the image make sure to resize it and move it to where you want. For resize there's no ability to ensure the proportions stay the same. Just eye it. Once you are done, it is in its own layer, which you cannot change. If you don't like how it ends up delete that layer and start again.

One handy thing is that you can use ctrl-c as soon as you resize it and then ctrl-v the next time you need to insert your image. Assuming you want the same size image this will save you some time.

When you are done choose File->Export to PDF to get it back into the PDF format I assume you'll want for sending your signed doc.

Note: A downside to Xournal is the finished document looks like the fonts are converted to an image. Fonts are no longer as crisp. Still it looks better than if you printed and rescanned and is much faster. [Note: in my most recent experience it seems this problem has been solved. Maybe I just got lucky with the particular fonts used. Please leave a comment abt your experience and I'll update accordingly.] This issue seems to be fixed in Xournal++ version 1.0.20.

Best Answer

Related Solutions

Ubuntu – Batch convert ai files to pdf / png etc

Ubuntu – How to edit a picture into an existing PDF file

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