|Python Imaging Library Handbook|
PIL reads and writes TIFF files. It can read both striped and tiled images, pixel and plane interleaved multi-band images, and either uncompressed, or Packbits, LZW, or JPEG compressed images. In the current version, PIL always writes uncompressed TIFF files.
The open method sets the following info properties:
(1.1.5) Image resolution as an (xdpi, ydpi) tuple, where applicable. You can use the tag attribute to get more detailed information about the image resolution.
In addition, the tag attribute contains a dictionary of decoded TIFF fields. Values are stored as either strings or tuples. Note that only short, long and ASCII tags are correctly unpacked by this release.