There’s this:
https://docs.juce.com/master/classDropShadowEffect.html
It looks pretty bad & isn’t very tweakable but it gets the job done efficiently.
There’s also Vinnie Falco’s library that contains implementations of all the Photoshop Filters you reference above — this looks great and is powerful, but it uses a very old version of JUCE and is very inter-dependent (aka you need to use the entire library to just get the photoshop parts).
I would love it if he rewrote that to work with modern JUCE, but I imagine that’s a large task and he’s busy doing other things (like making Boost awesome).
In my app I tried both, and neither were usable. The JUCE one looks like ass, and the VFLib came with too much extra baggage (some of it dates back to JUCE 2 even). I ended up manually adding very small gradient rectangles where I needed them.
This took forever, but looks very good!
I hope there is an improvement in JUCE regarding drop shadows soon.