21.8. imghdr — Determine the type of an image

Source code: Lib/imghdr.py

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

The imghdr module defines the following function:

imghdr.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 what():

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

imghdr.tests

A list of functions performing the individual tests. Each function takes two arguments: the byte-stream and an open file-like object. When 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('bass.gif')
'gif'