To See The World In A Gr^H^H Single Pixel

From last night's L&O:SVU[*]:

That's it? No porn? You're sure?

Just three cheesy pictures, totally innoccuous.

That doesn't make sense. Why would O'Donnell give Banks these pictures?

I didn't get it either, so I dug a little deeper, and found computer code hidden in a pixel. [zooms in one a tiny portion of the image, so each pixel appears as a square, then teensy text appears, line by line, within one square] I cracked it, I found a secret file, and found all these pictures.

Ripped me right out of the story, it did. Took my head away from the plot, and I spent the last 18 minutes of the episode stuck in can't-decide-whether-to-mock-or-gripe mode. Some writer -- no, make that every writer, the director, whover did the graphics for that scene, and anybody else who had a chance to look at that line -- apparently has heard of steganography but lacks not only any trace of a clue about how it works, but also a reasonable understanding of how raster image files work in general.

I'm pretty sure that if the cheesy picture had been stored with a colour depth of 640 bits per pixel[**] (instead of a more typical 24 bits), the police tech would have immediately noticed that a) the file was suspiciously large for that size picture, and b) ordinary image-handling software was confused by it. Is it just a super-geek thing, or were reasonably computer-literate non-geeks scratching their heads and thinking, "Wait, pixels don't work like that, right?" C'mon, there has to be at least one graphic artist working on that show who knows what a pixel is, whom they could've asked ...

Then again, in a genre (police procedurals / crime drama) where until recently it seemed that low-budget CCTV cameras all had infinite resolution as long as a detective kept asking a tech to zoom in a little farther[***], I guess the idea that any one pixel could hold arbitrary amounts of "computer code" is just more of the same kind of error...

Steganographic images are real, of course. Steganography[****] is not just used for sexy spy stuff and sleazy sex-crimes stuff like on the telly; it's also the technique underlying invisible digital watermarks (the kind where you don't see a distracting logo layered on the image, but where the person who stuck the watermark in can prove that you stole her photo even after you've cropped off the copyright notice and such). It doesn't hide a lot of info in one pixel. In a 24-bits-per-pixel image, human viewers are usually not going to notice tiny changes to low-order bits of the pixels, so you spread the hidden data out across several pixels, making the change to each pixel too small to attract attention.

Now if they'd just gotten that bit even almost right, they wouldn't have wrecked the last third of the episode for computer-literate people. There'd still be the problem of, say, a 4 GB flash drive large enough for thousands of photos and PDF files appearing to contain only three small images and almost no free space left, without that being a tip-off right there (or the writers could've made that the inspiration for the tech to check for hidden files and/or steganography!), but that's more of a 'fridge logic' problem than a point-and-laugh error.

 

Or am I asking too much?

[*] Law & Order: Special Victims Unit, "Hardwired"

[**] Rough idea based on how many dots representing the revealed computer code appeared in that one-pixel square, without bothering to rewind and watch more closely.

[***] Lately it seems the more common approach is to have the tech say, "I'll clean that up for you," and apply some math to the image to interpolate the desired data -- often a few steps better than what I suspect works in real life, but still blurry enough to not smack the casual viewer upside the head with the absurdity of it -- with the occasional infinite-resolution camera and a few cases of techs saying, "Well you know real cameras don't work like the ones on tee vee; this is as good as it gets," once in a while.

[****] Note also that steganography is not limited to images. Codes of the "take the first letter of every seventh word" count as steganography too. But on television, when steganography shows up it's usually in a photo or video.