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Writing a file sync app for smugmug -- Colorspace conversion is killing my Md5s!
horizon180
Registered Users Posts: 5 Beginner grinner
I have a basic, functional app for Windows built that allows you to scan folders on your computer and find which files you have not uploaded to smugmug yet. It does this by comparing the Md5 hash of the files. However, certain files undergo automated colorspace conversion, and they are changed as a result.
I've now enabled smugvault archiving for minor photo corrections, so the exact original is archived on smugvault.
The last piece of the puzzle is this: I need to be able to get the md5 sum from the smugvault file in order to match it to the file on disk.
This is especially important because many users will have photos with identical filenames, depending on how they import the files.
Right now, I don't see a way to get the smugvault file's checksum. I would love if I could get this information back in the smugmug.images.get API function (with heavy = true).
I've now enabled smugvault archiving for minor photo corrections, so the exact original is archived on smugvault.
The last piece of the puzzle is this: I need to be able to get the md5 sum from the smugvault file in order to match it to the file on disk.
This is especially important because many users will have photos with identical filenames, depending on how they import the files.
Right now, I don't see a way to get the smugvault file's checksum. I would love if I could get this information back in the smugmug.images.get API function (with heavy = true).
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I manually download each file after I've uploaded to my archive section and do a bit-by-bit compare, but an md5 would definitely be faster.
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If you pass 'true' to the 'Heavy' parameter of this api call, you get a whole bunch of the meta data associated with each file, including the Md5 sum.
http://wiki.smugmug.net/display/API/show+1.3.0?method=smugmug.images.get
... except it won't match your local copy if smugmug has converted the colorspace or rotated the image.
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Maybe it would possible for you to do an on the fly conversion to sRGB on your end and then compare the MD5 for your file to the one on SmugMug to see if it's a match in case the initial checksum doesn't match? This is just an idea and I have no clue if it's practically possible.
One other thing that you have to plan for is that we try to reduce files that are above our 24MB file limit to make them fit within our specs.
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It's quite simple to do in C# using System.Security.Cryptography.Md5 if you are familiar with programming. See http://msdn.microsoft.com/en-us/library/system.security.cryptography.md5.aspx
I don't know anything about colorspace conversion, if it requires re-compression, etc. I'm also not interested in changing any aspect of my files on disk. I just want to be able to back up the originals without thinking about it.
I really need access to the smugvault file metadata to do this cleanly. Otherwise, I may be stuck implementing more hackish methods of ensuring files are equivalent, like building a white-list for files that have been verified manually (ugh).
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Or another implementation is to generate the md5 and store in a local db as being uploaded. Then as you scan for new files, you simply compare SM's md5s with those in your local db.
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