Problem saving PDF to Gray Tone

Question

Level 1

14 points

Problem saving PDF to Gray Tone

I need to save a Black and White (more correctly Grey scale) version of a color newsletter PDF that I have for submission to a commercial printer. This used to be easy in older versions of Mac OS; I would simply do a "Save As" or "Export" and select the "Gray Tone" Quartz Filter and the result would be exactly what I need.

In recent versions of Mac OS (I think roughly from Mavericks on) when I do this, I get a mostly gray scale PDF, but some images in it are still in color. No combination of printing to PDF, saving as, or exporting will turn *all* the images in the document to black and white. It seems to be related to images that have a "shadow" effect applied in the original document (created in Pages). Can someone please tell me what's going on here, and how to create a gray-scale document from my color document? I've been able to do it with Acrobat Pro using the Gray Scale pre-flight fixup, but this *should* be possible with Preview, and I've no desire to purchase Acrobat Pro just for this 3-times a year requirement.

Thanks in advance for your help.

Rich

MacBook Air, OS X El Capitan (10.11.6), null

Posted on Aug 14, 2016 12:17 PM

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Answer 1

VikingOSX

Level 10

123,290 points

Aug 31, 2017 2:46 AM in response to open eric

It was intended to be helpful, and after I posted above, new information, and tools became available to me that verifies that Preview is no longer performing a complete grayscale conversion. It was never designed to be a prepress tool.

One must use Adobe Acrobat Pro, or Ghostscript 9.2.1 to obtain a complete grayscale conversion.

Acrobat Pro 10.1.4
Document Open > Left Toolbar > PDF Document Icon (bottom one) > Standards> Open Preflight > Profiles > PDF Fixups > click on Convert to grayscale > Analyse and Fix button (bottom right) > Name the file > Save
Ghostscript 9.2.1 (Terminal)
1. gs -sDEVICE=pdfwrite -sProcessColorModel=DeviceGray \ -sColorConversionStrategy=Gray -dOverrideICC -o out.pdf -f in.pdf
2. Now, verify the amount of CMYK in the out.pdf using the Ghostscript ink coverage device. A grayscale result will show the CMY values as 0 in the inkcov results.
  gs -o - -SDEVICE=inkcov out.pdf

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Answer 2

Aug 30, 2017 4:17 PM in response to VikingOSX

I can confirm this is not a helpful answer. To reproduce the problem, make a pdf file by exporting a document with color to PDF from Google Docs. The Quartz Filter will fail to convert the document to grey tone. (El Capitan 10.11.6 (15G1611))

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Answer 3

VikingOSX

Level 10

123,290 points

Aug 14, 2016 12:34 PM in response to rjb1

You are opening the PDF in Preview, and then selecting File menu : Export… as PDF, and choosing the Gray Tone Quartz filter?

The following are before and after using Preview. The third image is opening the PDF in Affinity Designer, selecting each image, and performing a new layer adjustment : Black and White to each image. Exported as press ready PDF.

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Answer 4

rjb1 Author

Level 1

14 points

Aug 14, 2016 12:36 PM in response to VikingOSX

VikingOSX wrote:

You are opening the PDF, and then selecting File menu : Export… as PDF, and choosing the Gray Tone Quartz filter?

Yes, as I said, I'm doing exactly that, and unfortunately it doesn't work. The resulting PDF is gray scale, except for the images which remain in color - it seems to be the images that originally had a shadow effect on them. Most frustrating.

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