I see that the calibre code when it does a conversion discards all of the guide reference entries which are of the "other." type. So if there are thumbnail images of various sizes etc they are all discarded.
e.g. after conversion, the following three will be removed
Code:
<guide>
<reference href="Images/sand_9781101140536_msr_cvi_r1.jpg" title="Cover" type="other.ms-coverimage-standard" />
<reference href="Images/sand_9781101140536_msr_cvt_r1.jpg" title="ThumbImageStandard" type="other.ms-thumbimage-standard" />
<reference href="Images/sand_9781101140536_msr_ppl_r1.jpg" title="PPCThumbnailImage" type="other.ms-thumbimage" />
and replaced with calibre's cover page:
Code:
<guide>
<reference href="Text/titlepage.xhtml" title="Cover" type="cover" />
I assume in theory I could just replace that top entry above for a minimal change to the ePub. Perhaps Kovid can tell me the rationale for removing all the other entries? Wondering whether I should do the same or not.