I am an RPG publisher and use Calibre to maintain my research library (PDF, mostly) and my stock art library (various image files).
When I load a PDF, Calibre automatically creates a cover image using the first page of the PDF.
When I load image files, it cannot. I must assign the cover image explicitly. Is there a way to have Calibre automatically create a cover image from a 'book' that is a raster image (JPG or PNG format)?