[GD-General] Dithering from 24-bit to 16-bit

[Tom H. <to...@ve...>]

I'm looking for a tool that will take a 24-bit RGB image and reduce it down 
to lower bit depths (specifically, RGBA_4444, RGB_565, and RGBA_5551) with 
nice dithering to attempt to preserve the image quality. The perfect 
solution would be a Photoshop plug-in that worked kinda like their 
posterize function, but supported different bit depths per channel and did 
dithering.

Tom