[magick-users] identify: What is signature,
and can it be used to recognize similar images?
glennrp at comcast.net
Sat Mar 15 21:47:55 PST 2003
At 07:14 PM 3/13/03 -0500, Michael Greisman wrote:
>I am interested in
>a) recognizing duplicate images and
>b) recognizing similar images.
>I noticed that ImageMagick's Identify command produces a signature
>for each image. Can you please tell me where I can find out how the
>signature is generated, and to what degree it identifies the image?
>I'm wondering if I can use the signature for recognizing duplicate
>and similar images.
Two images with identical pixel data, even if stored in different
formats, will produce the same signature. It is the SHA digest
computed over the pixels in a canonical form.
It is of no use in recognizing similar images; two images differing
only in one pixel will have entirely different signatures.
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