How to get file thumbnail from windows cache through python?

Question

Goal is to get files thumbnails from selected folder on windows in a minimum possible amount of time.

Imagemagick and other tools open files every time, so they may not be the most efficient. Built-in mechanism in Windows has a possibility that the thumbnails can be in cache, which theoretically gives a considerable speed boost.

From How to get thumbnail of file using the Windows API? (answer) it became clear about the ways, but there was a lot of problems:

• IThumbnailProvider and IThumbnailCache not found in:
  1. ctypes.windll.shell32 (there is only functions, and seems that there is no simple way to get interfaces)
  2. win32com.shell.shell (PyWin32)
• IID_IThumbnailProvider and IShellItemImageFactory through SHCreateItemFromParsingName and IID:

  1. That IID's not found in win32com.shell.shell, so they was provided manually.

  2. IThumbnailProvider, IShellItem::BindToHandler method: fixed, but now error is the same as below:

     # str(shell.IID_IShellItem) == '{43826D1E-E718-42EE-BC55-A1E261C37BFE}'
     # str(shell.BHID_ThumbnailHandler) == '{7B2E650A-8E20-4F4A-B09E-6597AFC72FB0}'
     
     item = shell.SHCreateItemFromParsingName(r'd:\some.png', None, str(shell.IID_IShellItem))  # str() is works
     IID_IThumbnailProvider = '{e357fccd-a995-4576-b01f-234630154e96}'
     provider = item.BindToHandler(None, shell.BHID_ThumbnailHandler, IID_IThumbnailProvider)  # error
     
     > TypeError: 'There is no interface object registered that supports this IID'
     

  3. IShellItemImageFactory: suspect that there is wrong usage of IID, but from answer below it should work:

     IID_IShellItemImageFactory = '{bcc18b79-ba16-442f-80c4-8a59c30c463b}'
     item = shell.SHCreateItemFromParsingName(r'd:\some.png', None, IID_IShellItemImageFactory)  # error
     
     > TypeError: 'There is no interface object registered that supports this IID'
     

It would be great to understand how to swim in all this without learning the whole winapi..

Thanks in advance.

Windows 10 (20H2), Python 3.9.5, PyWin32 301

---

Update: Found answer about PyWin32 (pythoncom.CoCreateInstance can't create IZoneIdentifier; the interface is missing from registry too despite being documented in MSDN). In short, these interfaces are not implemented. Checked by:

> import pythoncom
> pythoncom.InterfaceNames

So .. there are 2 questions left. Are there any options to get to thumbnails without using PyWin32? Via ctypes, for example. And how?

Answer 1

Here some working Python 3 code based on ctypes and comtypes:

from ctypes import POINTER, byref, cast, windll, c_void_p, c_wchar_p
from ctypes.wintypes import SIZE, UINT, HANDLE, HBITMAP
from comtypes import GUID, IUnknown, COMMETHOD, HRESULT

shell32 = windll.shell32
shell32.SHCreateItemFromParsingName.argtypes = [c_wchar_p, c_void_p, POINTER(GUID), POINTER(HANDLE)]
shell32.SHCreateItemFromParsingName.restype = HRESULT

SIIGBF_RESIZETOFIT = 0

class IShellItemImageFactory(IUnknown):
    _case_insensitive_ = True
    _iid_ = GUID('{bcc18b79-ba16-442f-80c4-8a59c30c463b}')
    _idlflags_ = []

IShellItemImageFactory._methods_ = [
    COMMETHOD([], HRESULT, 'GetImage',
        ( ['in'], SIZE, 'size' ),
        ( ['in'], UINT, 'flags' ),
        ( ['out'], POINTER(HBITMAP), 'phbm' )),
    ]

LP_IShellItemImageFactory = POINTER(IShellItemImageFactory)

def get_thumbnail(filename, icon_size):
    ''' Returns thumbnail image as HBITMAP'''
    h_siif = HANDLE()
    hr = shell32.SHCreateItemFromParsingName(filename, 0,
            byref(IShellItemImageFactory._iid_), byref(h_siif))
    if hr < 0:
        raise Exception(f'SHCreateItemFromParsingName failed: {hr}')
    h_siif = cast(h_siif, LP_IShellItemImageFactory)
    # Raises exception on failure.
    return h_siif.GetImage(SIZE(icon_size, icon_size), SIIGBF_RESIZETOFIT)

if __name__ == "__main__":
    h_bitmap = get_thumbnail(r'C:\test\test.jpg', 64)
    print(h_bitmap)