Any Python modules for manipulating JFIF file contents?

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  • Kenneth McDonald
    #1

    Any Python modules for manipulating JFIF file contents?

    Warning: this post may display my utter ignorance of image file format
    facts.

    As part of a photo album program I'm working on, I'd like to be able
    to work with the metadata in JPEG files, which I understand are
    really JFIF files holding jpg data. Do any Python modules permit
    me to do this? I looked at PIL, but it seemed to operatre at a
    higher level, i.e. hiding the file-level implementation details.

    At the least I'd like to be able to :

    1) Extract the metadata (comments, thumbnails, etc)
    2) Extract the raw JPEG data (since I want to experiment with
    combining multiple images into a single 'album' file using
    gdbm file.)

    Writing would be nice, but is not necessary.

    Failing a Python module, can anyone suggest the best library
    to look at to wrap in a module?

    Thanks,
    Ken McDonald
    Tags: None
    • Jeff Epler
      #2
      Re: Any Python modules for manipulating JFIF file contents?

      PIL can extract information like resolution.

      exifdump.py and EXIF.py can read the "EXIF" data that accompanies many
      photos taken on digital cameras. This can include a thumbnail,
      information like exposure time and focal length, and on some cameras it
      even tells you the orientation of the camera when the picture was taken.
      These two programs don't have any external requirements, they parse the
      JFIF and EXIF structures in pure Python.

      There are also Python wrappers for imlib and imagemagick, two other
      (unix) libraries often seen for image manipulation. I used imlib long
      ago, but I've never used imagemagick.

      My online photo albums (http://photos.unpy.net) use python with image
      metadata stored in a postgres database and the images themselves stored
      on the filesystem. It uses exifdump.py to read EXIF information. The
      source code to this is too nasty for me to consider sharing it with the
      world.

      More recently, I've been writing an image viewer in pygame, with the
      primary goal to reduce how often the user waits for a response. For
      instance, when the program is idle it preloads and scales the
      next/previous image in the image sequence. This has been fun (and I'm
      glad I learned pygame) but a user madly pressing "next" on an 800MHz
      machine can always get ahead of the computer trying to load 6 megapixel
      photos! To make things worse, PIL doesn't seem to release the GIL
      during long operations (such as loading a JPEG image or scaling it, each
      of which can take 2 seconds), and lacks progress callbacks (let alone a
      way to abort one of these operations in progress)...

      Have fun with your project!

      Jeff

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