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Recovering Blurred Text Using Photoshop and JavaScript
An anonymous reader writes "There's been a lot of talk about recovering blurred or pixelated text, but here's an actual implementation using nothing but Photoshop and a little JavaScript. Includes a Hollywood-esque video showing the uncovered letters slowly appearing."
From TFA:
Hey Timothy, are you trying to get the mac fans riled up?
I'd try this myself, but I stopped pirating PS at version 6. Be interesting to see what other Slashdotters make of this.
Linux, you magnificent bastard, I read the fucking manual!
Now for all of the other pixellated stuff...
Bwahahahaha.
BIG squares.
I never understood why people use pixel mis-mashing when they want to obfuscate something in an image.
drawing a big black rectangle is 10x faster and there is no way you can de-obfuscate that
Is it not the case that the reason this works is because you're running the -same blur algorithm- with the -same input- (the unblurred letters/pixels) and simply iterating through the letters and looking for equivalent output?
Presumably, the blur algorithm output could resolve such that multiple unblurred letters resolve to the same blurred pixels, but even if it is not this trivial to map the input state to output state, it still wouldn't seem to me to approach solving the general case of letters "blurred" by any arbitrary means, which is the real-world capability implied by the article.
What am I missing here?
~ Whence do you come, slayer of men, or where are you going, conqueror of space?
The article mentions the authors 'cheating a little' by de-blurring the image under 'ideal conditions'. From what I can gather, he is using a source Photoshop file (PSD) as the sample. If he already had access to the source PSD file, wouldn't it be easier to just click undo a few dozen times? Can this be reproduced to a raster image at all?
I judt got a nre Kinesis keybiartf so please excusr ant egregiou typos.
Jeez. Hasn't anyone seen CSI?
You're on the wrong forum for that line of reasoning. You'll want to find a site that's either anti-censorship or pro-porn. Good luck finding something like that on the internet.
"While my original goal of recovering the censored text on my friendâ(TM)s page was never achieved, the project was a success."
I wouldn't call that a success...
Good execution of a basic concept, but the fact remains that this shit is infeasible in practice. You have all the font issues (the typeface, the spacing, the color, the size, etc.), and you've got all the source issues - Are you sure that's text? Is it English? Was it obfuscated in other ways? Has the image been altered after the text was rendered? How has compression affected it?
The biggest fucking issue, of course, is that you're assuming the text was obfuscated using photoshop, or at least very similar blurring/pixelating algorithms.
It's a great project in terms of using javascript and photoshop to do something neat but basic in concept (essentially brute forcing, as the author says).
But unless you have inside info about how the text was rendered and obfuscated, you're better off taking a step back and squinting.
I think I see a duck.
If you know the blur algorithm, you can run each character through it to produce the blurred output, then compare that result to the image you are trying to unscramble and pick the closest match.
This assumes the blurring doesn't cause pixels to overlap their neighbors too much, that the algorithm produces deterministic output (isn't random), and that there are few possible inputs resulting in the same blurred output.
If the letters overlap because the blur blends with its neighbors then it just becomes a computational complexity problem where you have to try words instead of letters. A lot harder, but not totally impossible.
A blurring algorithm that used some large mosaic effect prior to bluring or used randomized input would produce a similar looking blur effect, but without disclosing much about the input.
Personally, I'd prefer examining the blur area for the predominant background color and create a gradient/mosaic around that color to fill the area. Then there is absolutely no chance of recovering information, but the effect on video wouldn't be too horribly jarring (as a black box might be).
Natural != (nontoxic || beneficial)
Actually the one on my site was written myself, and is located at http://tlrobinson.net/projects/js/jsdock.php It was written back in my early days of JavaScript, so it's probably not the prettiest code...
-tom
drawing a big black rectangle is 10x faster and there is no way you can de-obfuscate that
That's not entirely true. There was an article a couple years back about a technique for recovering redacted text with pretty high reliability.
It used the fact that most standard fonts have variable spacing, and that once you've determined the font you can model that only certain combinations of letters will actually fit in the space of the redacted word or words. Combined with a dictionary and bayesian matching based on nearby words, you can often figure out what words would have fit into a redacted rectangle. Or at least limit it to a fairly small pool of possibilities.
They demonstrated it on a redacted government document, and pulled out some places where the redacted words had to be "Iran" and "Ahmedinejad" etc., because nothing else both fit and made sense. If it's a monospaced font, you know the exact number of letters of the redacted text.
I can't find the original link, but here's a paper that describes some of the techniques available for "cracking" blackout redaction. (some apply only to magic-marker-type redaction, but others apply even to electronic black-rectangle redaction).
I stole this sig from someone cleverer than me.
I think people would be more interested if this removed the blur from nipples.