ghostscript convert color pdf to black and white

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Convert a PDF to greyscale on the command line in FLOSS?

I have a colour PDF file, and I'm going to print it out and then photocopy it in black and white. I'd like to know what it's like in B&W before photocopying it. Is it possible to 'greyscale' a PDF on the command line using free software? I'm using Ubuntu 9.10.

• command-line

3 Answers 3

ImageMagick can do this.

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• 38 That significantly reduces quality. @goyinux' solution is better. –  Johannes Weiss Feb 12, 2013 at 16:41
• 8 Convert will actually rasterize the contents of the pdf. So unless the pdf already encapsulates only raster images (e.g. a scanned document), this approach is a big no-no. –  m000 Sep 19, 2014 at 12:24
• 4 Unless you use -density 400 -quality 100 parameters - that works well –  burtek Dec 13, 2015 at 20:51
• 2 Really, is there anything ImageMagick can't do? :) –  Joshua Grosso Reinstate CMs Aug 18, 2017 at 3:02
• 1 -density 400 -quality 100 creates HUGE files. +1 for @goyinux's solution. –  Stanimir Stoyanov Jun 27, 2018 at 10:45

• 2 Agreed, this gives much better results than convert, but sometimes it rotates the pdf which is a bit annoying! –  tdc Aug 7, 2012 at 18:08
• 21 Just realised you can disable that with -dAutoRotatePages=/None –  tdc Aug 7, 2012 at 18:15
• 2 I just ran this command on a 58MB PDF that was already greyscale (came from a scanner) and the resulting output was 10MB and looked exactly the same. Nice! –  Archie Dec 19, 2012 at 2:33
• 1 Works well on Windows, too! Just remove the `\` and put everything on the same line. –  ixe013 Aug 19, 2014 at 4:23
• 1 In fact, this fails with this error GPL Ghostscript 9.10: Unable to convert color space to Gray, reverting strategy to LeaveColorUnchanged. –  jjmerelo Dec 15, 2015 at 17:56

Here’s a little script which in addition to the grayscale conversion can concatenate multiple input files. To use the script, put the following lines in a file, e.g. "convert2gray.sh"

and make it executable

will produce a single PDF "converted.pdf", which contains all pages from the input files converted to grayscale.

I had to print out mutliple files all in grayscale and found this the easiest way, since you can print out everything after inpection with one command.

• FWIW, pdftk can concatenate PDFs, too. –  user1338062 Jun 14, 2018 at 7:07

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bzxbot / Convert a PDF file to black and white (not grayscale)

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Convert PDF to black and white

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Maximum combined file size: 100MB, up to 50 files Supported types: PDF, DOC, DOCX, ODT, PPT, PPTX (all files will be converted to PDF automatically)

PDF to grayscale (b/w) converter

Free online tool for converting color PDF to black and white (grayscale). Upload PDF document and click convert.