Retroarch (RA) is a frontend for libretro, covers a lot of emulator cores and comes with tons of very good shaders, some of them made exclusively for RA (ehem libretro) as it offers the most advanced shader platform for retro gaming. Very popular and with active development.
The snippets are from the shaders itself, just grab a text editor. The viable tweaking options are declared as defines (
#define saturation 1.2 for example) and changing a number to a new usable value should produce the desired change.
I have included the saturation option in some of my shaders as they compensate for the higher output gamma. Dunno about the black point tweak though...