Date: Sun, 06 Sep 2009 13:34:17 -0400 From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> To: freebsd-questions@freebsd.org Subject: Re: Is there such thing as a 'soft checksum' tool? Message-ID: <44skf0c6zq.fsf@lowell-desk.lan> In-Reply-To: <64c038660909050933h25a91edcw56688993f5557ad2@mail.gmail.com> (modulok@gmail.com's message of "Sat\, 5 Sep 2009 10\:33\:03 -0600") References: <64c038660909050933h25a91edcw56688993f5557ad2@mail.gmail.com>
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Modulok <modulok@gmail.com> writes: > I'm not even sure such a tool exists, but it's worth asking: > > I'm looking for a pseudo-checksum tool for use with catalogging > images. For example, a strict checksum algorithm, like the sha family, > will produce a dramatically different checksum for two files which > differ by only a single bit. I'm looking for something where two > images images, which are similar, get a proportionally similar > checksum. When I speak of similarities I'm referring to their image > patterns. i.e two images of differing sizes, which are otherwise > identical, would produce very similar checksums. So the closer the > checksums are, the more similar two given images are. > > Does anyone know of anything like this? It turns out this is a remarkably hard problem. You can look at p5-Image-Compare, but be prepared to experiment before trusting the results. -- Lowell Gilbert, embedded/networking software engineer, Boston area http://be-well.ilk.org/~lowell/
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