Oversampling

[mbilotta]

This is a feature I'd really like and I think it should be possible to have it implemented without the need of support from representation plugins. Basically there should be a way to tell Julia to render 2, 3 or 4 times the size of the requested image and then scale it down averaging the colors inside blocks of 2x2, 3x3, 4x4 respectively. Of course this approach requires a huge amount of memory but could be applied to any representation transparently.