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Thai police have arrested a suspected paedophile who became the subject of an international manhunt. Interpol issued an unprecedented appeal for help after experts succeeded in unscrambling digitally-swirled images of the suspect, contained in depictions of the abuse of young boys posted online. Five different sources …

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Dan
Stop

Experts

Applying the swirl technique in reverse over a swirled image hardly represents the work of experts. I would have expected a tech-aware El Reg to report this in the same way as pouring scorn on the MoD or whoever for trying (and failing) to black out portions of PDF documents. Leave the ignorant 'expert' title for the mainstream media.

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3 years to reverse the swirl?

Why didn't Interplod 'experts' ask for some help from the Internet denizens if they were having so much trouble coding up a reverse swirl? That should've been done in three days.

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Law
Go

RE: Experts

There are loads of variables to consider when de-swirling an image... Joe Public normally doesn't have the expertise to run this sorts of filters many times over... plus we don't know how many times this guy applied different swirl operations on it and if he altered the settings.

Believe it or not, it's not all computers follow TV series examples where one algorithm fits all.... so yeah, experts might be a good enough term for them...

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Boffin

@Dan

You clearly haven't thought about the actual problem which has been solved. Go back to sleep.

The 'experts' will only have had a low-res lossy compressed image format (ie jpg) pulled off the 'net to work with. Since the swirl transform was more than likely generated from the original full-res original image, a large amount of the data needed to reverse the process will have been thrown away in the reduction/compression process when converting to jpg, making the recontruction process several times more difficult.

I'm guessing they will have had to run some fairly complex interpolation to reconstruct as close as possible the high-res image in order to get more than a smudge out of the reverse-transform process.

If you disagree, you'll find an example here: http://www.theregister.co.uk/2007/10/08/interpol_unscrambled/ ... have a go yourself and see.

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Just because experts did it doesn't mean they were the only ones that could

@Dan

Just because they used an "expert" doesn't mean they required one. It's twisting logic to say that because they didn't need an expert, that the people who did it were therefore not experts. Additionally an expert at un-swirling is just that and doesn't need to be some other type of expert in order to receive the title so long as the context is declared.

It's good to hear not all criminals who try to use technology to cover up their crime get away with it. It's also good to hear law enforcement have some basic tech skills themselves.

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Dead Vulture

hhhmmm

one has only to wonder what form the "questioning" will take in this unnamed thai gaol. perhaps there will be justice in the world when he's getting cornholed by the chief of thai ladypolice in some sweaty bangkok hell hole.

I do have to admit when i saw the pictures originally I wondered why noone had twigged onto running it back through photoshop to remove the swirl...not the greatest effort at disguising your identity!

Brings to mind the pixellation they put on your face when you get interviewed by panorama, but if you screw your eyes up just right.....;)

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Title

Actually, i dont care about the 'tech' arguments.

Just happy that technology has helped track down an alleged pedarist.

I hope that any court this individual may face provides appropriate justice.

If the allegations are true..one only hopes that this individual reaps what he has sown...

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Just unscrambled the pic myself

I downloaded and played with the image in Photoshop, just to see whether or not the descrambling was all tht difficult. I suspected it would be; my first suspicion was that the perpetrator, knowing he was creating photographic evidence of crimes, would at the very least use multiple passes of the filters he used to obscre his face, possibly with different selections or at different levels.

As it turns out, he didn't.

Anyone with Photoshop can do this, though getting results as good as Interpol's takes some precise work and jiggery. Still, in about five minutes (and working from the image posted on El Reg), I was able to get results almost as good as Interpol's.

If anyone cares about the technical details, he used the built-in Photoshop "Twirl" filter. You can undo it yourself in Photoshop. First, make a selection of the distorted part of the image. Use the oval marquee tool; I found it easiest to start from the center part of the twirl (the center of the eye) and expand the marquee outward rather than trying to freehand the selection. Bring the marquee right out to the outer edge of the distortion effect; I used the point at which the horizontal gold stripe of the wall pattern behind him begins to distort. The affected area is almost, but not quite, a perfect circle.

Then run the Twirl filter. Start with a setting of -999 degrees; he ran it originally at maximum effect. If you see asymmetric distortion of his face, your selection wasn't quite right; rejigger your selection a little bit, rinse, and repeat. You'll know you got your selection right on the money when his face magically appears out of the swirl.

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Thank you Franklin...

...For taking the time to prove what I thought was fairly obvious, and for providing sufficient detail for anyone interested to reproduce your results. Do those doubters (Law, Sean) wish to provide any follow-up sheepish responses?

So back to the main question:

Why did the 'experts' (sic) at Interplod take three years?

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Sci-Fi gets it wrong

In a Season 1 episode of the "new" Battlestar Galactica, the captain waits patiently as the ship's computer enhanced a surveillance photo so someone in the photo can be identified. Gimme a break: Their ships can time-warp but their computer needs hours to enhance a photo?

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