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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():
| 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 |
New in version 2.5: Exif detection.
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'