I kind of figured it was complex, but not THIS complex. Would you by any
chance have a link to a research paper - Though I highly doubt it ;) - that
would have something like this in it.
Does anyone think that there is some open-source way to accomplish it?
Sincerely,
Pierce F.
On 10/30/08 10:04 PM, "Graham Cox" <email@hidden> wrote:
>
> On 31 Oct 2008, at 2:21 pm, Pierce Freeman wrote:
>
>> Hi everyone. I am wondering if there is some way to compare two
>> images in
>> Cocoa, and then somehow spit out a percent of how similar they are.
>> The only
>> way I could think of is comparing every pixel, but this seems like
>> it would
>> take a long time, and even so I have no idea how to go about doing
>> that.
>
>
> It's non-trivial. Comparing each pixel doesn't really work. You could
> have two identical images but if one was shifted by just 1 pixel,
> you'd have almost no match even though to the eye they'd look the
> same. You can compare images for equality this way, but not similarity
> (i.e. if they are absolutely identical in every way you can tell, but
> the smallest difference means no match at all).
>
> Researchers have been looking into this sort of thing for years. There
> are ways to do it, but it requires some pretty heavy lifting in terms
> of breaking down an image into "features" then finding whether those
> same features can be found in the second image, regardless of how
> those features might have been transformed in size, position or angle.
> You can then come up with a figure for the number of feature matches
> and how these are different, and so arrive at a figure for the overall
> similarity of the two images. So, it can be done but you'll need to
> look at some serious academic papers to get a flavour for what's
> involved - it's almost verging on AI.
>
> Good luck ;-)
>
> cheers, Graham
>
>
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