I'm creating interior graphics for a client's nonfiction book and came across something I can't explain. I created a small, transparent graphic in Photoshop, exported it as a transparent PNG file (24-bit, not 8-bit), placed it in an InDesign document, and exported the document as a PDF/X-1a:2001. Everything looked fine in Preview, but if I import that PDF export back into Photoshop, for some reason my PNGs have grey backgrounds. What could cause that? If I sent the final PDF to the on-demand printer, would it print with the grey background, or would it read the transparency correctly?
I'm working on Mac Big Sur, Photoshop 22.5, and InDesign 16.3.2.
Attached is an example...
^^ This is the transparency as it's seen first in Photoshop.
Then this is what they look like when placed in InDesign. I have them on a larger grey background in the design, and these are actually still transparent.
This is what it looks like if the PDF is reimported into Photoshop. This is where it gets weird and I get the grey boxes. I've figured out why I'm getting thin white lines around the bounding boxes, but I can't figure out the grey issue.
Here's an example file of the PNG (which is only about half an inch wide due to project reasons).
One additional Edit: I'm realizing the boxes only show up if there's also a text field in the InDesign PDF export. If I just have the graphic and export it from InDesign, there's no problem.