At the moment the roseate multi-threaded down sampling function is only used via the zune-image backend. I'm looking to change this soon and use zune-imageprocs instead by default for down sampling on the zune-image backend.

As the roseate function won't be used by default anymore we'll need to add it as an image optimization.

[image.optimizations]
multi_threaded_sampling = { enabled = true }