My bet is a palette of 32 colours.

Here's my take on this.
Somehow I ended up with the same behaviour for BCns as Noesis.
SNorms - seems like a (channel_value+0x80) & 0xFF fix. - UPD: turns out no.
SRGBs... I don't think Noesis has gamma correction.

UPD: deleted, see Acewell's post

Well, I caved in to rewrite my 2016 QuickBMS script into a Noesis one. Automatic ZLIB handling - no need to decompress .tex files anymore. You'll have to remove conflicting scripts (in this case Acewell's tex_CompileHeart_PSVita_tex.py ). I'll update with decompression of Sting/Aquaplus implementati...

That's just zlib compression.

PCK is a game archive, in this case it's the same as Hyperdevotion Noire.
TEX are zlib'd and 8bit palletized, palette is right after the image data.
I didn't encounter 8bit palletized images in Hyperdevotion Noire PC back in 2016, so my script doesn't apply the palette.