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."

Comments

Ideal conditions

[Itninja]

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?

Yes, you can de-obfuscate black rectangles.

[IdahoEv]

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).