Yes, it's trivial. I've resized 4000 dpi 6x7 film scans to 800 pixel wide web images. Those start at around 9000 x 11000 pixels (bigger than the D800's native image size of 7360x4912), and the process is just the same as with smaller images. I'm not exactly the only person in the world who has shot and scanned medium format or larger film and then re-sized the images for the internet, so this isn't new. BTW, the quality looks great because the resampling process eliminated film grain visible in the larger images.