Re: md5_sum column - Developing command line tool for F-Spot

[Robert Latest <boblatest googlemail com>]

Hello all,

I'm currently developing a generic C library that will solve all these
problems. Actually I'm doing it for a different purpose that doesn't
have anything to do with images, but it'll work just as well. Some
charateristics:

- C library with dependency only on sqlite3 (so it can be easily liked
to any code)
- Synchronisation with minimal overhead (i.e., based on md5 sums the
code will be able to determine if a file has been copied, moved or
renamed)
- Generic library that can be used on any type of file

The idea is that if you muck around in your directory with other
tools, a quick synchronization will bring everything back in order,
and if a file's content doesn't change, neither will its ID, no matter
if it is renamed or moved.

The current, pre-alpha version of the code fully catalogs 22k photos
in less than 10 minutes on my six-year old, 1GHz/512MB machine. A
resync after adding or moving a few dozen files takes only a few
seconds.

This isn't magic, it's just that the f-spot code is extremely
inefficient. There's no point in creating a thumbnail image just to
get a signature on a file. I like f-spot's high-level GUI
functionality (myself I'm really bad at GUI coding), but the
nitty-gritty core stuff needs some serious help.

That said I'm not sure when my code will be far enough along to be let
out into the wild in any form. Don't hold your breath. I'll keep you
posted.

robert

On Sun, May 30, 2010 at 10:35 PM, Johan Zaxmy <johan zaxmy com> wrote:
> sön 2010-05-30 klockan 19:52 +0200 skrev Robin Clarke:
>> My problem: To search local files and identify whether they are in the
>> database yet, I want to create the md5 hash, and search the database for
>> this hash.  Problem is that the md5 hash I generate for a known image
>> doesn't come out the same as the one in the database.  I've heard that
>> it is just the image data which is used (without the meta data), but if
>> someone has some more specific information, that would be very helpful.
>
>
> This seems to be the c# code that generates the md5 sum. Hope it will
> help you...
>
>
>     public static string GenerateMD5 (SafeUri uri)
>      {
>         try {
>            if (md5_cache.ContainsKey (uri))
>               return md5_cache [uri];
>
>            using (Gdk.Pixbuf pixbuf = ThumbnailGenerator.Create (uri))
>            {
>               byte[] serialized = GdkUtils.Serialize (pixbuf);
>               byte[] md5 = MD5Generator.ComputeHash (serialized);
>               string md5_string = Convert.ToBase64String (md5);
>
>               md5_cache.Add (uri, md5_string);
>               return md5_string;
>            }
>         } catch (Exception e) {
>            Log.DebugException (String.Format ("Failed to create MD5Sum
> for Uri: {0}\n", uri), e);
>         }
>
>         return string.Empty;
>      }
>
> regards
> Johan, not a C# guru either
>
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