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Author Topic: Grayscale export  (Read 546 times)

StenP

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Grayscale export
« on: May 15, 2019, 02:35:05 pm »
Using Scribus 1.4.8 on windows 10:

Create a new document, 2 pages
Enable color management with default settings
Create a text box and insert sample text on first page
Create image box and insert grayscale image on second page
Export to PDF/X-3 with standard settings

Check PDF with Ghostscript inccov
 0.00000  0.00000  0.00000  0.02364 CMYK OK
 0.08084  0.08091  0.08091  0.02423 CMYK OK
The second page with the picture now contains color channels!

Is this a bug or am I doing something wrong? My intention is to export grayscale only.

utnik

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Re: Grayscale export
« Reply #1 on: May 15, 2019, 04:01:30 pm »
hi sten

…Is this a bug or am I doing something wrong? My intention is to export grayscale only.

i don't think of a bug here. as scribus doesn't convert any colors while exporting to .pdf/x-3 (the standard allows mixed color systems), your grayscale image will still be an rgb file…

what happens if you use 'item' → 'image effects' → 'grayscale' and export as a .pdf/x-1a? (i can't check it here – sorry!)

utnik

StenP

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Re: Grayscale export
« Reply #2 on: May 15, 2019, 04:29:46 pm »
Exporting PDF/X-1a with image effect grayscale actually works! But as soon as I try PDF/X-3 the color is back. Colud You please explain this in some more detail? Why the difference?

utnik

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Re: Grayscale export
« Reply #3 on: May 15, 2019, 05:17:37 pm »
hi sten

first the most essential part: every .pdf/x-1a file is a valid .pdf/x3 file (but not the other way round…)
  • the specifications for .pdf/x-3 allow mixed content (i.e. cmyk and rgb parts in the same file). that's the reason, why scribus won't convert any color while creating x-3 files.
  • in a .pdf/x-1a file all the content needs to be converted to the output profile. in this case scribus needs to care about the color conversion.
as your placed image is an 'rgb' file, there's no such thing as 'pure black'. (in the 'rgb' model 'black' means no color at all! – wich might be best represented in a rich black when converted to 'cmyk'…)

utnik