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DPChallenge Forums >> Tips, Tricks, and Q&A >> Modifying raw image "Exif" data
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 12/21/2006 11:34:15 AM · #1
For those "programmer" types out there I have a question I've been trying to find an answer to for several weeks now. I am trying to write a Visual Basic .Net 2005 application that will manage my photos. One of the features that I would like to build into the app is the ability to insert some "typical" data into the raw image's metadata ("Exif") such as photog name and contact info, copyright information, etc. My problem is that I have not found any resources that discuss how to access this infomration in a raw file. I can do it with a jpeg or tiff but not a raw file. I'm hoping someone on this list might have the knowledge I'm looking for or know of a resouce where I can find that infomration. Can anyone here help me out?

Thanks,
 12/21/2006 11:42:42 AM · #2
I don't think the owners or Site Council members will be too happy to see this thread. I'd advise you to organize your photos in jpg form since you know how to modify that info. Then simply insert the raw file identifier into the metadata of the associated jpg. That way you know which raw file was the source of the jpg and you maintain your original, unmodified raw files which is important on this site.
 12/21/2006 11:44:37 AM · #3
You really want to modify the IPTC info, not the EXIF information. IPTC is where things like keywords and descriptions get stored. I don't know if the ofset of the IPTC information is different fo a RAW file than a JPEG or TIFF, but in theory it shouldn't be. It should still be located in the file header.

Edit:
Apparently, RAW files, at least Canon RAW files, do not have IPTC fields. Interesting.

Message edited by author 2006-12-21 11:48:34.
 12/21/2006 11:44:48 AM · #4
Since there is not yet a RAW standard and all the RAW file types are proprietary, I doubt you are going to find much valuable info on this subject.
 12/21/2006 11:47:45 AM · #5
I know Iview uses a script to do the same thing. Is there any way you could copy one of the free scripts that is available for that program?
 12/21/2006 11:59:53 AM · #6
Take a look at dcraw.
It's written in C for Linux, but shouldn't be too difficult to deciper/port.

I would expect the exif standard to be implemented in the same way as jpeg/tiff images - in which case it will just be a case of finding the exif header and working from there.

I may have more references at home, will check later.
 12/21/2006 02:58:15 PM · #7
Originally posted by kirbic:
You really want to modify the IPTC info, not the EXIF information.


Yes it is the IPTC data that I am referring to. I use the "Exif" moniker to refer to the metadata. I even bundle the Adobe XMP information into that. I know it is technically wrong to refer to them that way but it seems that most people familiar with digital photography have an idea of what exif is but get a strange look when you say IPTC or XMP. Anyway, I do appreciate the input.

My desire is not to use this for images to be used in challenges here at DPC. It is two fold though. 1) This is mainly an exercise to learn VB in more detail as VB is utilized to quickly build applications to access data and do reporting in the industrial automation environment in which I have my day job. 2) I would like to have the application to help me manage my photos (i.e. where they are, when they were backed up, what the original source file was and its location, etc.).

It is true that there is no RAW standard but EXIF, IPTC, and XMP all are standardized. It may be that each of the camera manufacturers implement the standards in their own unique way but the data should still be accessible. You can get at the data with Adobe Bridge so there must be a way to do it. I know XMP has namespaces for Exif and IPTC data so Bridge may be using XMP to distribute data to the other metadata sections. I looked at the XMP SDK but it is in C++ and I̢۪m not familiar with C in anyway.

Thanks for the input. Hopefully I can find what I need.

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