Change superpixel size interactively

[Rexmiao]

It would be nice to change the superpixel size interaractively. however, its a bit tricky to implement since the superpixels are DL based, and thus require backend computation. so having e.g., a slider would not produce instantaneous superpixel size differences. one would need to select a size and then wait for the processing to take place. so its certainly do-able, just not sure how to make it elegant at the moment.