"imghdr" --- 推測圖片種類
*************************

**原始碼：**Lib/imghdr.py

Deprecated since version 3.11, will be removed in version 3.13:
"imghdr" 模組 (module) 即將被棄用（詳情與替代方案見 **PEP 594**）。

======================================================================

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

The "imghdr" module defines the following function:

imghdr.what(file, h=None)

   Test the image data contained in the file named *file* and return a
   string describing the image type.  If *h* is provided, the *file*
   argument is ignored and *h* is assumed to contain the byte stream
   to test.

   在 3.6 版的變更: Accepts a *path-like object*.

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 檔案                           |
+--------------+-------------------------------------+
| "'rast'"     | Sun Raster Files                    |
+--------------+-------------------------------------+
| "'xbm'"      | X Bitmap Files                      |
+--------------+-------------------------------------+
| "'jpeg'"     | JPEG data in JFIF or Exif formats   |
+--------------+-------------------------------------+
| "'bmp'"      | BMP 檔案                            |
+--------------+-------------------------------------+
| "'png'"      | Portable Network Graphics           |
+--------------+-------------------------------------+
| "'webp'"     | WebP 檔案                           |
+--------------+-------------------------------------+
| "'exr'"      | OpenEXR 檔案                        |
+--------------+-------------------------------------+

在 3.5 版被加入: 新增 *exr* 與 *webp* 格式。

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.

範例：

   >>> import imghdr
   >>> imghdr.what('bass.gif')
   'gif'
