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I am currently realizing a poster with Scribus (I am a beginner) and run into troubles while printing with black background.

I have several pictures with transparent backgrounds (png). First, the general background of the document was set to cyan and there was no problem. Everything printed fine. Now I switched to a black background and here started the problems. All my pictures appear on print to be frame with black which is slightly different that of the background one (not the case in the pdf).

full poster zoom on a box

I am printing after export to pdf using my office printer: export pdf export pdf printer properties

I tried several thing which did not work.

  • Created my own black with 100% K -- no improvement
  • Used Rick black -- worst: contrast is even more marked
  • Downloaded Scribus 1.5 to export to PDF X-4 -- no improvement
  • Checked all pictures properties for knock out properties
  • Switch to overprint properties -- no improvement
  • Activated color management -- but there I am not sure what to do further...

color management

I guess it's not a transparency problem as everything works fine when background is cyan, and I am completely stuck so any help/suggestions would be welcome on this.

Thanks!

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PNG (and RGB) can be really fine in a print workflow.

Of course, if you want to be sure that the colors are matching, you'll have to setup a color managed workflow (and activate the color profiles).

Now, you're not saying how you're printing. One important thing: always first create a PDF and then print that PDF. You should probably not directly print from Scribus.

If you're printing on a home / office laser printer, you should probably go for a PDF 1.4. You mention that you tried PDF X-4. That should also work with PNG and transparencies (as far as I know, it's based on 1.4). But the whole printing workflow should then really support PDF X-4.

On the other side, if you want to switch to a CMYK workflow, you can use a TIFF with transparencies. Or fill the background with the same color as you have in the final document (and change the frame's shape in Scribus so that you don't hide parts of your document).

Finally, I've done a lot printing on office printers with PDF 1.4, PNGs and transparencies and I never had any issues. But it was almost always on white backgrounds.

There is one thing you have to make sure: the whole printing workflow should support PDF with transparencies (or you should have a "clean" flattening at some time). When a ripper flattens a PDF, it normally does it in a "stupid" way and you simply get a solid color.

Edit (since I cannot upload files in a reply):

I've now created a transparent PNG with a black rectangle filling part of it and a black RGB shape in Scribus that is below the image. Here is the PNG file:

a black rectangle

I cannot upload here the SLA (scribus 1.5) and PDF:

On screen, they look fine to me. Can you try to print the PDF on your printer?

  • To answer you I updated my question with more info and how I printed. I believe that my workflow does support transparency as I have no problem printing on cyan background. I know I could fill my backgrounds with black to solve the issue, but I would prefer to not use a work around and completely understand (and solve) the problem. – Xochitl C. Apr 23 '18 at 9:19
  • can you also upload somewhere the image that shows the issue? and maybe a .sla with only this image and a black background that prints incorrectly for you? but it won't be easy to debug for me, since i currently don't have access to a printer (similar to yours). – a.l.e Apr 23 '18 at 10:51
  • See my edit above for a set of test file I've created for you to test (PNG, SLA, PDF). – a.l.e Apr 23 '18 at 11:13
  • I export file from the sla to pdf and printed it and got the same problem, so it could be my printer. I do not manage to get your pdf file (sla is suggested), could you upload it again? Thanks again for all your help! Here is your square file I exported to pdf (framadrop.org/r/…) – Xochitl C. Apr 23 '18 at 12:41
  • Btw everything looks fine on screen and pdf reader (your files and mines) – Xochitl C. Apr 23 '18 at 13:19
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PNG images are RGB, they are for use on the web/rgb displays, not for print. The format doesn't support CMYK.

Use a CMYK TIFF instead, and make sure the TIFF's black background is the same CMYK mix as the black background in your document.

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