symbian-qemu-0.9.1-12/python-2.6.1/Doc/library/imghdr.rst
author johnathan.white@2718R8BGH51.accenture.com
Mon, 08 Mar 2010 18:45:03 +0000
changeset 46 b6935a90ca64
parent 1 2fb8b9db1c86
permissions -rw-r--r--
Modify framebuffer and NGA framebuffer to read screen size from board model dtb file. Optimise memory usuage of frame buffer Add example minigui application with hooks to profiler (which writes results to S:\). Modified NGA framebuffer to run its own dfc queue at high priority


:mod:`imghdr` --- Determine the type of an image
================================================

.. module:: imghdr
   :synopsis: Determine the type of image contained in a file or byte stream.


The :mod:`imghdr` module determines the type of image contained in a file or
byte stream.

The :mod:`imghdr` module defines the following function:


.. function:: what(filename[, h])

   Tests the image data contained in the file named by *filename*, and returns a
   string describing the image type.  If optional *h* is provided, the *filename*
   is ignored and *h* is assumed to contain the byte stream to test.

The following image types are recognized, as listed below with the return value
from :func:`what`:

+------------+-----------------------------------+
| Value      | Image format                      |
+============+===================================+
| ``'rgb'``  | SGI ImgLib Files                  |
+------------+-----------------------------------+
| ``'gif'``  | GIF 87a and 89a Files             |
+------------+-----------------------------------+
| ``'pbm'``  | Portable Bitmap Files             |
+------------+-----------------------------------+
| ``'pgm'``  | Portable Graymap Files            |
+------------+-----------------------------------+
| ``'ppm'``  | Portable Pixmap Files             |
+------------+-----------------------------------+
| ``'tiff'`` | TIFF Files                        |
+------------+-----------------------------------+
| ``'rast'`` | Sun Raster Files                  |
+------------+-----------------------------------+
| ``'xbm'``  | X Bitmap Files                    |
+------------+-----------------------------------+
| ``'jpeg'`` | JPEG data in JFIF or Exif formats |
+------------+-----------------------------------+
| ``'bmp'``  | BMP files                         |
+------------+-----------------------------------+
| ``'png'``  | Portable Network Graphics         |
+------------+-----------------------------------+

.. versionadded:: 2.5
   Exif detection.

You can extend the list of file types :mod:`imghdr` can recognize by appending
to this variable:


.. data:: tests

   A list of functions performing the individual tests.  Each function takes two
   arguments: the byte-stream and an open file-like object. When :func:`what` is
   called with a byte-stream, the file-like object will be ``None``.

   The test function should return a string describing the image type if the test
   succeeded, or ``None`` if it failed.

Example::

   >>> import imghdr
   >>> imghdr.what('/tmp/bass.gif')
   'gif'