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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=None)
     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    .. versionchanged:: 3.6
     24       Accepts a :term:`path-like object`.
     25 
     26 The following image types are recognized, as listed below with the return value
     27 from :func:`what`:
     28 
     29 +------------+-----------------------------------+
     30 | Value      | Image format                      |
     31 +============+===================================+
     32 | ``'rgb'``  | SGI ImgLib Files                  |
     33 +------------+-----------------------------------+
     34 | ``'gif'``  | GIF 87a and 89a Files             |
     35 +------------+-----------------------------------+
     36 | ``'pbm'``  | Portable Bitmap Files             |
     37 +------------+-----------------------------------+
     38 | ``'pgm'``  | Portable Graymap Files            |
     39 +------------+-----------------------------------+
     40 | ``'ppm'``  | Portable Pixmap Files             |
     41 +------------+-----------------------------------+
     42 | ``'tiff'`` | TIFF Files                        |
     43 +------------+-----------------------------------+
     44 | ``'rast'`` | Sun Raster Files                  |
     45 +------------+-----------------------------------+
     46 | ``'xbm'``  | X Bitmap Files                    |
     47 +------------+-----------------------------------+
     48 | ``'jpeg'`` | JPEG data in JFIF or Exif formats |
     49 +------------+-----------------------------------+
     50 | ``'bmp'``  | BMP files                         |
     51 +------------+-----------------------------------+
     52 | ``'png'``  | Portable Network Graphics         |
     53 +------------+-----------------------------------+
     54 | ``'webp'`` | WebP files                        |
     55 +------------+-----------------------------------+
     56 | ``'exr'``  | OpenEXR Files                     |
     57 +------------+-----------------------------------+
     58 
     59 .. versionadded:: 3.5
     60    The *exr* and *webp* formats were added.
     61 
     62 
     63 You can extend the list of file types :mod:`imghdr` can recognize by appending
     64 to this variable:
     65 
     66 
     67 .. data:: tests
     68 
     69    A list of functions performing the individual tests.  Each function takes two
     70    arguments: the byte-stream and an open file-like object. When :func:`what` is
     71    called with a byte-stream, the file-like object will be ``None``.
     72 
     73    The test function should return a string describing the image type if the test
     74    succeeded, or ``None`` if it failed.
     75 
     76 Example::
     77 
     78    >>> import imghdr
     79    >>> imghdr.what('bass.gif')
     80    'gif'
     81 
     82