Source code: Lib/imghdr.py
imghdr module determines the type of image contained in a file or
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
||SGI ImgLib Files|
||GIF 87a and 89a Files|
||Portable Bitmap Files|
||Portable Graymap Files|
||Portable Pixmap Files|
||Sun Raster Files|
||X Bitmap Files|
||JPEG data in JFIF or Exif formats|
||Portable Network Graphics|
New in version 3.5: The exr and webp formats were added.
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
The test function should return a string describing the image type if the test succeeded, or
Noneif it failed.
>>> import imghdr >>> imghdr.what('bass.gif') 'gif'