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:
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|
|'rast'||Sun Raster Files|
|'xbm'||X Bitmap Files|
|'jpeg'||JPEG data in JFIF or Exif formats|
|'png'||Portable Network Graphics|
You can extend the list of file types imghdr can recognize by appending to this variable:
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.
>>> import imghdr >>> imghdr.what('bass.gif') 'gif'