[IPOL discuss] Repository of test images

[Nicolas Limare]

> Well, for those images taken directly from the camera we have all
> that information, but some of the images might be altered before
> they can be used as test images. [...] But still the image has been
> taken with some parameters that perhaps are interesting to say
> (hoping that this doesn't confure the users). The original camera
> configuration and the transformations done afterwards.

If the dataset is published as an article, it will be the reviewers'
job to verify that all the possibly useful information is provided,
and that this information is clearly explained.

> According to the Wikipedia "SHA-1 appears to provide greater
> resistance to attacks[citation needed], supporting the NSA's
> assertion that the change increased the security". Anyway, we just
> want to use the hash function as a quick verification of the file,
> so I think it's enough. And it's very simple for the users to check
> a file. For example, using "shasum" in a GNU/Linux system.

Yes, we don't need cryptographic strength, just a quick and easy way
to verify that we got the good file. I still think providing SHA1 and
MD5 is better because it costs nothing to he authors and it provides
the users with whichever hash they are used to manipulate. But this is
not an important issue, and here again it should be decided by
editors/reviewers.

> If we proposed a new format to verify the contents of the file, it'd
> be more difficult for the users to verify the files.

I agree. I was just asking the question by curiosity, but this would
not be practical for people using these files and checksums.

> you have an input PNG image and you want to verify that it's exactly
> the same image used in IPOL.

(Here, you verify the checksum of the FILE, not the checksum of the
IMAGE. You could have different FILES, with different checksums,
containing exactly the same IMAGE. For example, files with a different
text comment. But let's close this pointless and unproductive
discussion on file vs image, I should not have raised it :)

-- 
Nicolas LIMARE - CMLA - ENS Cachan         http://limare.perso.math.cnrs.fr/
IPOL - image processing on line                          http://www.ipol.im/
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