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What was done right or wrong technically in this digital unmasking?

 
 
Jeanette Guire
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      10-16-2007
I'm curious what was technically done right (by Interpol) and wrong (by the
suspect) in this modern-day digital unmasking?
http://images.ctv.ca/archives/CTVNew...ile_071008.jpg

Full story here
http://www.ctv.ca/servlet/ArticleNew...1008?hub=World

What were the techniques used to mask and unmask the perp?
 
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frederick
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      10-16-2007
Jeanette Guire wrote:
> I'm curious what was technically done right (by Interpol) and wrong (by the
> suspect) in this modern-day digital unmasking?
> http://images.ctv.ca/archives/CTVNew...ile_071008.jpg
>
> Full story here
> http://www.ctv.ca/servlet/ArticleNew...1008?hub=World
>
> What were the techniques used to mask and unmask the perp?



It was done using a "whirl and pinch" filter. So long as
you line up the center and diameter, you can quite
effectively "unwhirl" the distortion using the same filter,
fiddling with the controls with "preview" on.
With the image size on the link, chances aren't good to get
anything like the detail shown in the "unwhirled" image, but
I could unwhirl it reasonably well. I guess that the
authorities had a larger image than this to work with?

The suspect appears not to have considered this.
Pixellation would have been much more effective.



 
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bugbear
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      10-16-2007
Jeanette Guire wrote:
> I'm curious what was technically done right (by Interpol) and wrong (by the
> suspect) in this modern-day digital unmasking?
> http://images.ctv.ca/archives/CTVNew...ile_071008.jpg
>
> Full story here
> http://www.ctv.ca/servlet/ArticleNew...1008?hub=World
>
> What were the techniques used to mask and unmask the perp?


Some convolution kernels are reversible, some aren't.

Try googling those words.

motion blur is a famous example of a filter
that is (counterintuitively) reversible.

BugBear
 
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timeOday
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      10-16-2007
bugbear wrote:
> Jeanette Guire wrote:
>> I'm curious what was technically done right (by Interpol) and wrong
>> (by the
>> suspect) in this modern-day digital unmasking?
>> http://images.ctv.ca/archives/CTVNew...ile_071008.jpg
>>
>>
>> Full story here
>> http://www.ctv.ca/servlet/ArticleNew...1008?hub=World
>>
>>
>> What were the techniques used to mask and unmask the perp?

>
> Some convolution kernels are reversible, some aren't.
>
> Try googling those words.
>
> motion blur is a famous example of a filter
> that is (counterintuitively) reversible.
>
> BugBear


I don't see how swirling could be accomplished by convolution. Care to
explain or post a link?
 
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