I don't know if I am going to be explaining this so it makes sense, but I have found that the Nook Color doesn't seem to "like" the file structure of epub files generated by Caliber as much as it does those generated by Sigil.
For instance, when I reconverted epub-to-epub using Calibre alone (which puts all the epub text/files into one main folder as you can see when you explode the epub, and generates sometimes color.jpeg or color1.jpeg files, don't know why the difference), the NC still won't recognize the cover art on many occasions, even when adding the "cover=ID" line).
However, if I
1) first open the epub in Sigil (make any changes I want or not), and save the epub again, and
2) THEN go to Calibre and convert epub-to-epub (which puts the text/files into separate directory folders), and
3) make sure there is both a copy of cover.jpeg and cover.jpg in the same directory as the content.opf file AND in the Images directory folder that was generated, and
4) make sure both of these lines are in the manifest of the opf file (I know both is probably overkill, but, hey...it covers all the bases for me)
<item href="cover.jpeg" id="cover" media-type="image/jpeg"/>
<item href="cover.jpg" id="cover" media-type="image/jpeg"/>
Then, when the book is downloaded to the NC, it will recognize the cover art every single time, without even having to reboot my Nook.
The key is to open and then save the epub file in Sigil BEFORE reconverting it in Calibre and making sure the jpg/jpeg files are in their proper locations in the epub directories, adding the lines to the opf file and rebuilding the epub. Does that make any sense? Maybe Calibre ought to see about formatting their epub files using the same directory structure as Sigil does???
Last edited by leday; 12-05-2010 at 10:29 PM.