2

Because printing an entire book in color is more expensive, I am trying to deliver greyscale PDFs to the printer, without success:

  1. I convert image to greyscale in Paint.net or Photoshop Elements. Save image as JPEG. (I also tried IrfanView.)
  2. Mount the image on a page in Scribus.
  3. Export as PDF from Scribus.
  4. Test ink coverage with Ghostscript. For a file where the First page contains an image, and the second page does not, this results in something like:

    c:\>C:\"Program Files"\gs\gs9.27\bin\gswin64c.exe -q  -o - -sDEVICE=inkcov Bwtest.pdf
    
     0.09917  0.09917  0.09917  0.10612 CMYK OK
    
     0.00000  0.00000  0.00000  0.05997 CMYK OK
    

The color channels are still there, thus making it a color image although it appears as greyscale. How do I make an image true greyscale without color channels? Can the JPEG format even contain an image with only greyscale, or should I use some other format?

1

Gray is not the same as gray...

You are only delivering unsaturated images. But that does not really matter.

The point should be on your step

  1. Export as PDF from Scribus

The settings you are using could be something like "convert images to CMYK" and they should say something like "export images as grayscale"

You can have any image, including full-color images, and when these settings applied, they will be converted to grayscale on the PDF conversion. Search there.


Should I use some other format?

The file format is (ouch) irrelevant. Let me explain. You are not having compression artifacts issues. That would be the case for an over compressed jpg image.

But the PDF holds the images within the self, and yes, it can have the same type of JPG compression as external JPG files. But again, this is irrelevant.

Setup your output to ZiP compression, so the PDF files will have lossless compression.


But a JPG file done right can be a good output file. If you want to go for the safe route use TIF files as middle process images.

  1. Get your original images, wherever they come from (yes probably a JPG file)

  2. Convert them to grayscale, save them as TIF... or PNG, or PSD, or whatever lossless file format you want) So you do not have "additional" compression.

  3. Put them inside Scribus, export a PDF file and now, the middle process file format is irrelevant, because, again, the images are inside the PDF file itself.


Can the JPEG format even contain an image with only greyscale?

Yes, it can.

  • Ok, thanks for pointing me to the right direction. However I found info about Scribus that it does not support grayscale conversion in the current version. The images must be grayscale already when I put them into Scribus. Is there a way to detect if a jpeg is grayscale only? – Sten May 1 at 15:39
  • 1
    Finally I realize that even if the original picture is grayscale, it is converted to RGB-channels on export from Scribus:-( Found a utility that can convert the final PDF to grayscale but it has a lot of limitations. – Sten May 1 at 17:22
-1

For myself, I prefer to use .png files for print output - supports greyscale perfectly, and is non-lossy compression, so no junky output.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.