Showing too much 'skin' detection in software

Question

I am building an ASP.NET web site where the users may upload photos of themselves. There could be thousands of photos uploaded every day. One thing my boss has asked a few time

Answer 1

I'm afraid I can't help point you in the right direction, but I do remember reading about this being done before. It was in the context of people complaining about baby pictures being caught and flagged mistakenly. If nothing else, I can give you the hope that you don't have to invent the wheel all by yourself... Someone else has been down this road!

Answer 2

Interesting question from a theoretical / algorithmic standppoint. One approach to the problem would be to flag images that contain large skin-colored regions (as explained by Trull).

However, the amount of skin shown is not a determinant of an offesive image, it's rather the location of the skin shown. Perhaps you can use face detection (search for algorithms) to refine the results -- determine how large the skin regions are relative to the face, and if they belong to the face (perhaps how far below it they are).

Answer 3

As mentioned above by Bill (and Craig's google quote) statistical methods can be highly effective.

Two approaches you might want to look into are:

• Neural Networks
• Multi Variate Analysis (MVA)

The MVA approach would be to get a "representative sample" of acceptable pictures and of unacceptable pictures. The X data would be an array of bytes from each picture, the Y would be assigned by you as a 1 for unacceptable and a 0 for acceptable. Create a PLS model using this data. Run new data against the model and see how well it predicts the Y.

Rather than this binary approach you could have multiple Y's (e.g. 0=acceptable, 1=swimsuit/underwear, 2=pornographic)

To build the model you can look at open source software or there are a number of commercial packages available (although they are typically not cheap)

Because even the best statistical approaches are not perfect the idea of also including user feedback would probably be a good idea.

Good luck (and worst case you get to spend time collecting naughty pictures as an approved and paid activity!)

Answer 4

I would approach the problem from a statistical standpoint. Get a bunch of pictures that you consider safe, and a bunch that you don't (that will make for a fun day of research), and see what they have in common. Analyze them all for color range and saturation to see if you can pick out characteristics that all of the naughty photos, and few of the safe ones have.

Answer 5

I doubt that there exists any off-the-shelf software that can determine if the user uploads a naughty picture. Your best bet is to let users flag images as 'Adults Only' with a button next to the picture. (Clarification: I mean users other than the one who uploaded the picture--similar to how posts can be marked offensive here on StackOverflow.)

Also, consider this review of an attempt to do the same thing in a dedicated product: http://www.dansdata.com/pornsweeper.htm.

Link stolen from today's StackOverflow podcast, of course :).

Answer 6

We can't even write filters that detect dirty words accurately in blog posts, and your boss is asking for a porno detector? CLBUTTIC!