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Re^4: Matching Images

by LanX (Canon)
on Nov 22, 2010 at 14:31 UTC ( #872974=note: print w/ replies, xml ) Need Help??


in reply to Re^3: Matching Images
in thread Matching Images

> and used an image editor to convert it to a compressed but lossless .png.

my point was that in "reality" lossless conversions are the exception and not the rule. IIRC the compression factor of a JPG is freely choosable.

Cheers Rolf


Comment on Re^4: Matching Images
Re^5: Matching Images
by BrowserUk (Pope) on Nov 22, 2010 at 14:40 UTC
    my point

    If information is "lost" through a lossy conversion, the images are different, and the code I posted will detect those differences.

    Note well: The OP didn't ask to find images that "looked the same" or were "substantially similar", or any other form of fuzzy comparison.

    He asked for:

    I would like my script to compare two images and tell me if even one single pixel is slightly different in one of them.

    Which is exactly what the code I posted--as opposed to your theory--does.

    Hence, your "point" is pointless.


    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.
      Funny, this subthread is a good example for aggressiv arguments. =)

      Cheers Rolf

      PS: BTW I'm off ... 8)

      UPDATE:

      > He asked for:

      > I would like my script to compare two images and tell me if even one single pixel is slightly different in one of them.

      Indeed! But he didn't talk about different image formats either, leaving much place for interpretations and clarifications.

        If by that you mean direct, forthright and accurate. Then yes, guilty as charged.

        Of course, such directness wouldn't be necessary if:

        1. people read the questions, that the answers they challenge are addressed to, before challenging them.
        2. made some attempt to verify their theories before posting them.
        3. didn't continue to argue in favour of those theories long after they have been disproved.

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