Image crossing spine on PDF export bug, summary.

When you place an image against the spine (X position 0) then export to PDF, the image may encroach a few pixels onto the opposite page. I've experimented, and here is how the bug behaves:

1. If you export spreads to PDF, an image against the spine may expand a couple of pixels into the opposite page.

2. This bug does not override layer priority. That is, an image on one side will not encroach a higher-priority image on the other side.

3. If you export pages (Ie., not spreads), the image may still be expanded, but instead of crossing the spine, a 3-pixel sliver will appear on the opposite side.

4. The 3-pixel sliver is ONLY created by an image on the left page, encroaching on the right page. It never goes the other way. (That is, a right-page image will not create a sliver on the left page.) This asymmetry is not observed when exporting spreads.

5.  This bug looks like a rounding error. However, it still occurs if exported images are not downsampled, and it cannot be fixed by setting image resolution to avoid rounding. (For example, the problem still occurs if the raw image is 5 inches at 600 PPI, fit exactly to its frame, and the PDF output image is 5 inches at 150 PPI.)

6. The problem can be fixed by moving images .0001 inches from the spine. Synthetic spreads still output correctly (I.e., no gap on the spine.)

I use Indesign CC, fully updated.

This bug may be related to the master-image bug, where master images against the spine will cause the opposite-side master image to appear when it shouldn't.