There are times when OCR doesn’t help e.g. handwritten Kanji and you need to search for Kanjis by hand (eyes).
About7-8 years ago http://jlex.org/search/parts was great
but since it’s demise a while ago it was difficult to find a good online alternative.
Now it seems http://kanji.sljfaq.org/radicals.html
has upgraded to the same level as Jlex.org with
http://kanji.sljfaq.org/mr.html
I’ve found the zKanji open source project at
http://zkanji.sourceforge.net/
It’s one of the best I’ve seen and for free at that. However, it has not been updated for years and it’s kind of complicated due to large functionality.
http://kissako.it/content/kanji-study-software-zkanji-1-minute-glance