Image Synthesis from Yahoo's open_nsfw
Warning: This post contains abstract depictions of nudity and may be unsuitable for the workplace
Yahoo's recently open sourced neural network, open_nsfw, is a fine tuned Residual Network which scores images on a scale of to on its suitability for use in the workplace. In the documentation, Yahoo notes
Defining NSFW material is subjective and the task of identifying these images is non-trivial. Moreover, what may be objectionable in one context can be suitable in another.
What makes an image NSFW, according to Yahoo? I explore this question with a clever new visualization technique by Nguyen et al.. Like Google's Deep Dream, this visualization trick works by maximally activating certain neurons of the classifier. Unlike deep dream, we optimize these activations by performing descent on a parameterization of the manifold of natural images. This parametrization takes the form of a Generative Network, , trained adversarially on an unrelated dataset of natural images.
The "space of natural images", according to , look mostly like abstract art. Unsurprisingly, these random pictures, lacking any kind of semantics, have low scores on the classifier.
 D(x) = 0.003 |  D(x) = 0.06 |  D(x) = 0.07 |  D(x) = 0.02 |  D(x) = 0.003 |
NSFW Images
Following Nguyen et al., we perform projected gradient descent on the following problem
to obtain the maximal activation for . Not surprisingly, the results of the optimization are clearly pornographic.
 D(x) = 1 |  D(x) = 1 |  D(x) = 1 |  D(x) = 1 |  D(x) = 1 |
 D(x) = 1 |  D(x) = 1 |  D(x) = 1 |  D(x) = 1 |  D(x) = 1 |
 D(x) = 1 |  D(x) = 1 |  D(x) = 1 |  D(x) = 1 |  D(x) = 1 |
 D(x) = 1 |  D(x) = 1 |  D(x) = 1 |  D(x) = 1 |  D(x) = 1 |
SFW Images
On there other end of the spectrum, optimizing for SFW images seem redundant, as you might just expect it to be the absence of NSFW content. If this were the case, one would expect to observe most images scoring close to . This is only kinda true. Random images generally score between . This is small, but not . We will try to push this down further by descending on
in the exact same way as above.
Images which maximize the this score all have a distinct pastoral quality - depictions of hills, streams and generally pleasant scenery. This is likely an artifact of the negative examples used in the training set.
