Re: image hashes

[Alvaro del Castillo <acs openshine com>]

Hi John!

The MD5Sum is a patch that I have already done in June for implement the
duplicate photo detection feature as you can read in F-Spot list:

http://mail.gnome.org/archives/f-spot-list/2005-June/msg00046.html

Cheers

El sáb, 13-08-2005 a las 17:14 +0100, John Leach escribió:
> Hi,
> 
> could f-spot store a hash (say SHA1) of each photo in the database? This
> would help f-spot recognise images even if their filename+path is
> changed.  It could be of use in 3rd party programs too.  for example:
> 
> I have a big directory structure of photos on my home computer which
> I've imported into f-spot and set some tags and descriptions etc.  So
> now I have an sqlite database with all this info in, identifying photos
> by their path and filename.
> 
> I sftp upload a selection of these photos to my web host.  Now all these
> images have a different file path (especially as I choose not to have
> anything like the same hierarchy on my web host).
> 
> I'd like to write a web gallery for my uploaded photos, and use the
> f-spot database for metadata.  If the sqlite database had hashes in, I
> could upload my photo.db and run a python script which would match up
> the new filepaths.
> 
> I realise this is rather a specialist setup, but I'm sure the hash would
> be useful for other things (I'd like to see f-spot recognise duplicates
> on import and keep their metadata in sync, for example).  My guess would
> be the overhead would be minimal, as each image ends up in the
> page-cache anyway from the thumbnailing process.
> 
> I've hacked up an sin-ugly patch to give me a SHA1 hash for testing
> (attached).  (It's my first ever c# code and I know very little about
> how f-spot works tbh).  It generates the hash in the Create method of
> PhotoStore (which is probably the wrong place to do it) and opens the
> file an additional time (which is probably unnecessary).
> 
> To test my patch you'll need to alter your table structure to add the
> 'digest' field to the 'photos' table (or kill your photos.db and it'll
> create a correct new schema).
> 
> It might not have to be a cryptographic hash, it could just be some
> other unique identifier that can be derived from the image file.  Exif
> seems to have a unique ID field, but I've not found a photo containing
> one yet.
> 
> Any thoughts?
> 
> Thanks in advance,
> 
> John.
> http://johnleach.co.uk/photography/
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