JPEG recreated at each start

[SR-G]

Even when defining a data dir, thumbnails are always recreated.

Steps to reproduce :

• start program with the --tempdir data/ flag
• all books are indexed / thumbnails are created
• stop the program, the log 2017/12/30 21:17:50 Not removing temp dir because dir already existed at start is dumped (quite expected)
• data/ folder still contains all *.jpg
• start the program again with the same command line / same --tempdir
• everything is indexed again (maybe expected) but every single thumbnail is then also recreated (which takes quite some time with a lot of *.epub)

(a test like "if the corresponding cover and thumbbail jpeg are already available in the current tempdir, then don't recreate them" is probably missing)

With BookServer 3.0.4

[pgaskin]

Thanks for reporting these issues!

As for caching, I forgot to add the check. Good catch.

[pgaskin]

I have fixed this, and it will be included in the next release. As for performance, there is not any noticeable difference unless you have a large number of books.