Support upscaling

[sindresorhus]

It would be useful if this package came with a .upscale() method as it's quite a common need to upscale the image after generating it. For example, using https://github.com/Stability-AI/stablediffusion#image-upscaling-with-stable-diffusion

[3DTOPO]

+1

The Unet architecture in x4-upscaling.yaml looks very similar to the Stable Diffusion model (v2-inference.yaml) so should be pretty straightforward but getting all the way to inferencing in Swift is a bit beyond my skill set. I'm more than willing to help and learn though.

[julien-c]

similar issue over at huggingface/swift-coreml-diffusers#7

Note that there's an implem in https://github.com/huggingface/diffusers so this should be a good first issue 👍

[3DTOPO]

Yeah that would be me. Their version of SD for  relies on the conversion scripts from this repo though.