Transparency error in Pre-flight?

[Dr Mick Mach]

I'm preparing to send a illustrated middle grade reader to print (Ingram Spark).  However, I did a pre-flight and for the first time selected 'Images' in the check panel.

Now every image in the book is being flagged with this error message:

Problem: Object has transparency applied

Fix: Edit the source file to remove all transparency.

All the illustrations in the book are simple black line drawings done in Photoshop.  (examples below) All the pictures where placed into my CC library and then placed into Indesign from there. Several of them have layers, but they don't have any effects such as drop shadow or glow.

Things I've tried from forum trawling so far:

Flattening the image in PS

Adding a white background layer in PS and naming it 'Background'.

Flattening the image in PS with a white background.

Checking the transparency in Indesign (nothing to tweak it's all set to opaque).

I'm quite new to indesign, so there's obviously something conceptual regarding this transparency issue that I'm not grasping, hence why I'm finding it so hard to solve.

However - do I even need to address this issue? IngramSpark states that all they need for the interior content is 'a print ready pdf' preferably 'in PDF/X-1 format.'

Possible to ignore and just export as pdf from Indesign?

Any thoughts or help appreciated thanks

Example of pictures in book (from indesign) and how the layers look (from Photoshop)

 

[BobLevine · Accepted solution]

Export using the PDF/X1-a preset. That will flatten everything and eliminate any transparency.

[Dr Mick Mach]

Awesome thanks Bob.

[Test Screen Name]

You say you did a preflight but who specified the rules to check for? Preflight does tests. what it finds is only a problem if the workflow says so.

[Dr Mick Mach]

Yeah it was my first effort at using pre-flight for more than just text over set, so didn't realise I could set the image parameters and it was checking for everything hah. Now I realise that transparency isn't going to be an issue with the pdf export, I worked out how to turn it ff.

[Test Screen Name]

But you shouldn’t turn it off! Not unless the printer needs you to. You diminish the quality.

[Dr Mick Mach]

Sorry, I don't mean I turned off the transparency, I just turned off pre-flight checking for it.

[Laubender]

Hi,

you'll see the transparency warning in the moment you place PhotoShop files with an additional layer to the background layer that is not flattened. That implies and introduces transparency to an InDesign document. Even if it is one "normal" layer and no pixels are actually transparent.

What could be done?
Convert to Grayscale and on to 1-Bit bitmap and save as tiff.

Then all drawing pixels come in with swatch [Black] when placed with InDesign and all non-drawing ones simply are "not there". This is looking like "transparency", but it does not invoke the transparency warning.

You can color the 1-Bit bitmap with InDesign. If you leave it with swatch [Black] make sure you set the image to overprint if you use it stacked above a colored background.

Regards,
Uwe