drMerry - I will take a look at your changes once 0.7.53 goes out. Kovid has made some changes which will allow scanning pdfs with the new pdf engine for just a selected number of pages from the front and back. We will have to see whether that significantly improves the performance or not. My initial testing of scanning the whole document actually found that the new engine is currently slower than the existing one, but that should change when not doing the whole document hopefully.
In terms of options to check numbers on technical manuals etc, I don't see where the issue will be. You say there will be more "errors" - do you mean more matches that are rejected? The logic I have will remain the same in terms of stopping searching after finding a valid ISBN. So surely the only issue will be for a manual that does not have an ISBN but does have lots of numbers in it will run slower? If I am able to somehow try to only scan a small front/back portion of all books (not just pdf ones) that shouldn't be an issue. I will look into that.
As for all the variations of ISBN being split across lines - I will be honest with my selfishness and repeat my statement above that I really don't care if there are really badly scanned documents that this fails to pickup an ISBN from. It is just a tool, not a miracle worker
. If your ISBNs are so badly formatted the rest of the content of that document will surely also be dire - not getting an ISBN may force you to open it and see for yourself and perhaps either decide to look for a better copy or edit it.
I don't want to have a whole bunch of options on this plugin, it is why I have resisted putting a menu onto it as there are too many permutations. I think of how I see people using it - they will give it a one click shot at trying to find an ISBN, and after that they will use a metadata download type lookup based on title/author matching. I really don't see them wasting a lot of time bothering making multiple attempts on the same book using different options? If it fails and they believe there "really must" be an ISBN in there, they will view the book and type it in if it means that much to them (which they will have to do for any graphical based PDFs anyways).
However that is just my opinion on how I see people using it.
If it handles 98% of the book ISBNs out there that is still an improvement without it.