For those baffled like me, the feature in Preview is under Tools->Annotate->Signature->Create... However, I could not figure out how to get the drawing to appear. The signature field either had an unmoving dark blotch or remained blank. For one moment, I saw an outline of my chest, shoulders, & chin that appeared and froze in place. The camera seems to be fixed on a low, zoomed-in spot at chest level - about where you might hold a piece of paper. No matter how much I bent over and waited, I could not get a properly framed drawing of myself to appear. My bet is that you need proper lighting for it to work as described.

I think this may be an "accidental" feature, i.e., the developers didn't plan for it to happen.

Preview is clearly doing some rather basic image processing to enhance the signature that you are expected to present to the camera. Things like converting to B/W, enhancing the contrast, probably some border enhancement, etc. If you apply those same image processing algorithms to any photograph sometimes you end up with extremely cool and even borderline-artistic representations of the photograph. That is probably what @chaunceyjb is seeing.

But I guess the developers didn't intend that use. In fact, I believe that they first run an algorithm that tries to determine if the image the camera is seeing is likely to be a signature or simply an image of the user while he is preparing the signed sheet of paper, so as to avoid producing a potentially confusing non-signature image.

I think that is the reason why neither @robleach nor I were able to get the hint to work: it is not supposed to work, and it did for @chaunceyjb because he tried it under unusual conditions that confused the first algorithm (the one that validates the signature).

Too bad, because the hint sounded cool.

That is a bummer, because this sounded really slick.

If it turns out the hint doesn't really work, I'll remove it.

Craig A.

I can't get it to work either. I've always wanted a drawing and haven't found a way to do it.

This worked for me: Hold a blank sheet of white paper just below the blue line. Make sure there's lots of light on you and the paper. After a couple of seconds, the "signature" image of your face appears.

Worked for me too, after a while. The white paper trick is key, or have a very light background. The app is clearly expecting paper, so presenting a high key image is a must

Don’t delete the hint, it works. I’ve been using this for years! Makes it so much easier to "sign" a document. You can place and zoom your signature wherever you like and then just write a PDF to send on its way.

Okay, this does work, and it's very cool--it's not just a high-contrast version of the image, it actually does some sort of edge-detection and smoothing algorithm that produces what looks impressively like a lineart drawing.

I found it very difficult to get it to kick in on a face, however. At minimum, it needs a very high-contrast background--stand in front of something white. It also seems to work better if there's nothing higher-contrast to distract it in your clothing--a dark shirt, for example--so either cover up all your clothes or wear something white. And as suggested, holding something in front of you that covers your body below the blue line also seems to help it kick in.

What I can't figure out is if it's actually doing a face-detection algorithm as well, in order to actively avoid a person's face--it seemed to more readily kick in with my hand than my face even though I have dark hair. People having trouble with it might if anything be because it's recognizing them as a face, and it only works when for a moment it fails to notice that there's a person in the frame.