[Stable UI] preview generation

[Riztard]

Feature request
add preview feature like the one from daniandtheweb/sd.cpp-webui . with that we can see some of the shape early like pose or landscape or if the frame cut face or other info. that way dont need to wait for the generation completed to check some info. even more if using slow hardware like me. would save time

[LostRuins]

This might be a consideration however it is quite expensive to do intermediate decoding + passing the data for the preview back and forth. So this might not be a thing anytime soon

[Riztard]

i believe the proj one is not that expensive since my old rx 580 didnt feel it. but the other preview mode is expensive. only cause some at max ~+10sec from the normal total time usually more than 2min. also is it not already implemented from Stable-diffusion.cpp? i thought we only need to change the front-end

also i think the proj one only outputting preview. that way it didnt need to do back and forth. maybe thats why its cheap

Looks like it is implemented in stable-diffusion.cpp? Disabled by default. Could a toggle be added, to enable it at-will?