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      1 :mod:`imghdr` --- Determine the type of an image
      2 ================================================
      3 
      4 .. module:: imghdr
      5    :synopsis: Determine the type of image contained in a file or byte stream.
      6 
      7 **Source code:** :source:`Lib/imghdr.py`
      8 
      9 --------------
     10 
     11 The :mod:`imghdr` module determines the type of image contained in a file or
     12 byte stream.
     13 
     14 The :mod:`imghdr` module defines the following function:
     15 
     16 
     17 .. function:: what(filename[, h])
     18 
     19    Tests the image data contained in the file named by *filename*, and returns a
     20    string describing the image type.  If optional *h* is provided, the *filename*
     21    is ignored and *h* is assumed to contain the byte stream to test.
     22 
     23 The following image types are recognized, as listed below with the return value
     24 from :func:`what`:
     25 
     26 +------------+-----------------------------------+
     27 | Value      | Image format                      |
     28 +============+===================================+
     29 | ``'rgb'``  | SGI ImgLib Files                  |
     30 +------------+-----------------------------------+
     31 | ``'gif'``  | GIF 87a and 89a Files             |
     32 +------------+-----------------------------------+
     33 | ``'pbm'``  | Portable Bitmap Files             |
     34 +------------+-----------------------------------+
     35 | ``'pgm'``  | Portable Graymap Files            |
     36 +------------+-----------------------------------+
     37 | ``'ppm'``  | Portable Pixmap Files             |
     38 +------------+-----------------------------------+
     39 | ``'tiff'`` | TIFF Files                        |
     40 +------------+-----------------------------------+
     41 | ``'rast'`` | Sun Raster Files                  |
     42 +------------+-----------------------------------+
     43 | ``'xbm'``  | X Bitmap Files                    |
     44 +------------+-----------------------------------+
     45 | ``'jpeg'`` | JPEG data in JFIF or Exif formats |
     46 +------------+-----------------------------------+
     47 | ``'bmp'``  | BMP files                         |
     48 +------------+-----------------------------------+
     49 | ``'png'``  | Portable Network Graphics         |
     50 +------------+-----------------------------------+
     51 
     52 .. versionadded:: 2.5
     53    Exif detection.
     54 
     55 You can extend the list of file types :mod:`imghdr` can recognize by appending
     56 to this variable:
     57 
     58 
     59 .. data:: tests
     60 
     61    A list of functions performing the individual tests.  Each function takes two
     62    arguments: the byte-stream and an open file-like object. When :func:`what` is
     63    called with a byte-stream, the file-like object will be ``None``.
     64 
     65    The test function should return a string describing the image type if the test
     66    succeeded, or ``None`` if it failed.
     67 
     68 Example::
     69 
     70    >>> import imghdr
     71    >>> imghdr.what('bass.gif')
     72    'gif'
     73 
     74