The authors of the paper have successfully conducted the attack on 227*227 images as well. The pixels are much harder to see with the human eye. It seems that

The authors of the paper have successfully conducted the attack on 227*227 images as well. The pixels are much harder to see with the human eye. It seems that larger images increase the search space as a linear function of the dimensions. That is to say, it does take more time to find such pixels, but they are still relatively common.