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13.6 Standard module imghdr

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

The imghdr module defines the following 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 what:

``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 JIFF format

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

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('/tmp/bass.gif')
'gif'