Remove "_" and "." with rename preset

How to (I don't understand the regexp-thing!)?

Regular expression rename from

(.)(-|.)(..[^.]+)#

to

\1\3

Or, if you want to remove the . in the file extension as well, then change the from string to:

(.)(-|.)(.)#

Thanks Leo, I really need to spend some time for this...

Just to say that leo's regexp replace . and - instead of _

So Sasa if you want to replace _ change to (.)(_|.)(..[^.]+)#

(_|.) mean search _ or .
You can replace others characters by adding characters separated by | in parenthesis.