MacOS Preview image missing from Saved ePub

[Jeffrey.Hallett]

Hi. Usually when I save an ePub to MacOS, a Preview image is automatically generated based on the cover image. This is the image that is shown in the Preview section of the Get Info and appears as the icon in Finder when an icon is not set (the files have no icon other than the system one).
Recently I changed the cover image on one of my books. This ended up being a bit of a trial and error, so I'm sure I broke something along the way. When I saved this updated book to disk, there was no preview image. All I saw in Finder was the generic ePub icon.
I've double-checked the metadata, manifest, cover.html, and image file. They seem to be correct. The cover shows up in the metadata just fine, and when I load the file itself into Books, for example, the cover does show correctly.
Can someone with more experience than I please point me to what correction I might make to get Calibre to properly generate the Preview image when the book is saved (I'm sure Calibre does generate it because it's a variant of the cover, not an exact reproduction of the cover image)
Thanks in advance! Jeff

[kovidgoyal]

calibre does not generate preview images. Never has. That will be something else on your system, likely a plugin for finder.

[Jeffrey.Hallett]

Thanks for that. It isn't a plug-in, but I did a bit of experimentation today and it seems the preview was created by Pages, the app that I used to create the original ePub. This leads me to believe that the original ePub file is still used by Calibre and for certain changes, Calibre simply updates the contents of the original file and reuses it. Changing the cover (or something else I did) was a 'breaking change' so Calibre generated an entirely new file that did not have the preview. Can you, or someone, confirm or deny this behavior?

[kovidgoyal]

Not sure what you mean making any change to an epub generates an entirely new file. Covers certainly dont make any "breaking" changes any more than any other kind of change. If you have some epub file for which Pages is not generating thumbnails that is most likely a bug in Pages and should be reported to Apple.

[Jeffrey.Hallett]

Hi, so no, I don't think there is a bug here on anyone's part. I may not be explaining well, so let me take a step back.
* I create my ePub originally in Apple Pages application. Those ePub files have a preview that is derived from the cover image.
* I import into Calibre to make a few small tweaks. I can look in the Calibre Library folder and see that even after making these few tweaks, the ePub file still has the preview image. I think the file is being updated with my edits, not rewritten.
* When I do Save to Disk, the saved file also has the preview image. That all works as expected.
* However. This is the first time I tried to update the cover image for an imported book in Calibre. After doing so, the preview image on the file was lost in both the Calibre Library file and the Save to Disk copy.
So it makes me think that when I do simple edits, those are being saved in place in the ePub in the Calibre Library folder. However, when I replaced the cover image, which updated the metadata and the cover.html and the manifest, the ePub file must've been rewritten instead of just updated and the preview was lost.
Anyway, this is me just trying to understand what happened, not implying any bug happened or anyone was at fault. I can send screenshots to demonstrate, but the pattern just leads me to think that certain changes will cause the ePub file in the Calibre Library to be rewritten instead of just updated.

[BetterRed]

Try unchecking the Update metadata embedded in the book when opening setting in Book Editor preferences (it's in the Edit menu drop down).

BR

[JSWolf]

Stop using Pages. It creates some rather messy Apple specific code.