I would like to view full cover of pdf ebook originally purchased on Kindle Store and then converted with Ultimate. I see the thumbnail on my adobe reader app on my ios device. I would like to know how to extract the cover image as I would like to read the editorial details on the expanded cover. The full cover image is not viewable in the Kindle App (even on original file), Adobe Acrobat, or Foxit PDF. It is puzzling that I can only view this on the acrobat reader app on my ios device. Please advice how to view and/or extract full cover image.
You can create an image of the page you desire to be displayed as the cover, and then have
calibre use that image as the cover.
If you already have an image, then open the metadata editor and on the right side of that pop-up notice that under the cover image is a button to browse. Use that to select your desired image.
In your case, you don't yet have an image and I understand that you want to use a particular page of the e-book. What follows is a simple one-liner for the linux (debian) command-line using
mutool from package
mupdf-tools; if you don't use linux, it may be that the exact same package / program exists for your operating system, or you can look for a corresponding command...
mutool draw -o "OUT-%d.png" IN.pdf PAGE-NUMBER
OUT is your desired output filename,
IN.pdf is your ebook, and
PAGE-NUMBER is the page number of your desired cover.