When calculating the exact likelihood, why you do not add uniform noise to the input image?

[huanranchen]

Hi~ According to the definition of bpd We should calculate the likelihood of x+u to approximate the bpd.

However, in this code, it directly calculate the likelihood of x instead of x+u. I test some image, and it even give me negative bpd (which means the probability of generating such image is greater than 1). Is this wrong?