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

Discussion in 'Digital Photography' started by Jeanette Guire, Oct 16, 2007.

  1. Jeanette Guire, Oct 16, 2007
    #1
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  2. Jeanette Guire

    frederick Guest

    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/CTVNews/img2/20071008/450_ap_pedophile_071008.jpg
    >
    > Full story here
    > http://www.ctv.ca/servlet/ArticleNe...08/pedophile_search_071008/20071008?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.
    frederick, Oct 16, 2007
    #2
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  3. Jeanette Guire

    bugbear Guest

    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/CTVNews/img2/20071008/450_ap_pedophile_071008.jpg
    >
    > Full story here
    > http://www.ctv.ca/servlet/ArticleNe...08/pedophile_search_071008/20071008?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
    bugbear, Oct 16, 2007
    #3
  4. Jeanette Guire

    timeOday Guest

    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/CTVNews/img2/20071008/450_ap_pedophile_071008.jpg
    >>
    >>
    >> Full story here
    >> http://www.ctv.ca/servlet/ArticleNe...08/pedophile_search_071008/20071008?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?
    timeOday, Oct 16, 2007
    #4
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