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Dull colors in PDF export--RGB to CMYK conversion problem
http://gimpchat.com/viewtopic.php?f=8&t=19653		 Page 1 of 1
Author:  Rita [ Wed Oct 13, 2021 3:39 pm ]
Post subject:  Dull colors in PDF export--RGB to CMYK conversion problem
GIMP Version: 2.10.24
Operating System: Windows
OS Version: 10 home
GIMP Experience: Intermediate Level


I need to export a file as a pdf for a print project, but no matter what I do, the pdf comes out with all of the colors dulled, especially the brighter ones. I don't know if I'm doing something wrong in Gimp, or if this is a pdf issue. [Everything I found online is from years ago and from people using PS.] I am working with a new file with everything flattened, so there is no issue due to layers. The image looks great as a jpg or a png, but I have no choice--I can only submit a pdf.

resolution is 300 px/in
mode is RGB
precision -- I've tried 8 bit and 32 bit with no difference
color management is enabled

I'm not sure what other settings to play with or list here.
Author:  Tas_mania [ Wed Oct 13, 2021 5:25 pm ]
Post subject:  Re: Dull colors in PDF export
Looks like you are exporting from Gimp to PDF?
When you say 'a new file with everything flattened' what sort of file?
Author:  Rita [ Wed Oct 13, 2021 5:29 pm ]
Post subject:  Re: Dull colors in PDF export
I created a new from visible, opened a new Gimp file, and copied it over so that the file I was working from had only the one layer.

I knew that exporting pdfs didn't play well with layers and transparency, so that was my work around.

When I export either jpgs or pngs from this file, they're perfect.
Author:  dinasset [ Wed Oct 13, 2021 11:31 pm ]
Post subject:  Re: Dull colors in PDF export
Try using IRFANVIEW for exporting an image in PDF.
Author:  AdmFubar [ Thu Oct 14, 2021 1:23 am ]
Post subject:  Re: Dull colors in PDF export
What are you using to print the pdf? Have you tried with color management off?
Author:  rich2005 [ Thu Oct 14, 2021 2:27 am ]
Post subject:  Re: Dull colors in PDF export
Quote:
I need to export a file as a pdf for a print project, but no matter what I do, the pdf comes out with all of the colors dulled, especially the brighter ones....snip.....The image looks great as a jpg or a png, but I have no choice--I can only submit a pdf.


Very probably the PDF viewer is applying settings (or not) More generally all about colour models.

When you view the image as a jpg/png on a computer it uses RGB and for most users the computer screen brightness is set way too high.

When printed the image is converted to CMYK colour and the 'gamut' - the range of colours is less than for RGB and no boost from the computer display. https://en.wikipedia.org/wiki/Gamut

RGB colors that you can see on your monitor (in particular, blue, green and all bright vibrant colors) cannot be printed and/or replicated with standard CMYK inks

You can get an idea of what a print will look like in Gimp by setting up soft proofing in Edit -> Preferences -> Color Management and View -> Color Management. (and preferably calibrate the computer display)
Author:  Rita [ Thu Oct 14, 2021 8:42 am ]
Post subject:  Re: Dull colors in PDF export
Thanks. I agree it's an issue of RGB to CMYK conversion.

I have tried the following:

1) Downloaded Cyan and ran it 1st from Gimp and a 2nd time by itself. Still not great results. Does anyone know if there are PDF parameters I could import into Cyan for better results?

2) Opened a png of the file in Krita and converted. Still didn't like the result, but I've never used Krita before so it could be me. Exported as a psd from Gimp, opened in Krita, and converted. Same result, though I could perhaps manipulate layers.

3) Trying Scribus to convert to a pdf. I'd read it had excellent pdf handing. If so, I'm not finding it.

I really want a Gimp answer. I would like to set up a soft proof that I can edit like rich2005 said. I will try to do that, but if anyone has any advice on freeware and good CMYK conversion, I would love to hear it. Thanks, everyone.
Author:  rich2005 [ Fri Oct 15, 2021 5:40 am ]
Post subject:  Re: Dull colors in PDF export--RGB to CMYK conversion problem
No replies ? Here is my two euros worth.

Quote:
I really want a Gimp answer. I would like to set up a soft proof that I can edit like rich2005 said. I will try to do that, but if anyone has any advice on freeware and good CMYK conversion.


I would just send your RGB PDF off to the printing company, as long as you realise that the printed version will have muted colours. If the printer needs CMYK then the best for designing is Krita in CMYK mode...but Krita does not export to PDF.

You can convert a CMYK image to a PDF using ImageMagick. A straight forward

Code: Select all
magick cmykimage.jpg  cmyktype.pdf


Using Gimp to soft-proof.
Not great and from experience not always accurate. However some hints here: https://youtu.be/awAeITMTWsQ along with Cyan, ImageMagick and Scribus. Why Scribus ? It does make good PDF's and if you have any text then Scribus text entries are correctly embedded in the PDF. Not always the case with Gimp pdf.
Author:  Rita [ Fri Oct 15, 2021 9:39 am ]
Post subject:  Re: Dull colors in PDF export--RGB to CMYK conversion problem
Thanks rich2005!

I wish I could send the RGB file, but that's a no go for Amazon. PDF only.

Thank you so much for the video. I downloaded the Adobe ICC profiles and used one of them to do a soft-proof. Amazon doesn't say what ICC profiles they use, so I had to guess. I chose Coated FOGRA27. I see that you have a different profile set.

I will play more with Krita and Scribus. Your video was a real help.

I do have one extra question about Gimp scrambling text when it makes a PDF. [I'm working with a completely flattened image to make the PDF, not the original file with separate text layers. I will not be able to add text in Scribus because I have done text effects such as beveling, etc.] I have not seen any scrambling yet. Is this something that happens when printed or would it also show in the PDF file? Thanks again.
Author:  rich2005 [ Fri Oct 15, 2021 10:27 am ]
Post subject:  Re: Dull colors in PDF export--RGB to CMYK conversion problem
Quote:
I do have one extra question about Gimp scrambling text when it makes a PDF. [I'm working with a completely flattened image to make the PDF, not the original file with separate text layers. I will not be able to add text in Scribus because I have done text effects such as beveling, etc.] I have not seen any scrambling yet. Is this something that happens when printed or would it also show in the PDF file?


Yeah, Amazon publishing has some odd requirements. Flattening the image before exporting to PDF is the way to go when using Gimp. It might have improved (not checked it yet) with Gimp 2.10.28 but the font metrics are not saved in the Gimp PDF file which results in a substitution (default) font used. Since you have applied text effects that text layer is rasterized anyway, no longer text, not a problem.

best of luck
Author:  Rita [ Fri Oct 15, 2021 10:55 am ]
Post subject:  Re: Dull colors in PDF export--RGB to CMYK conversion problem
I had flattened because I knew PDFs didn't handle transparency and various layer modes well. Good to know it also solves the text issue.

Thanks again for all your help!
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