FrameAware.apply_to_frames aborts entire thumbnail on a single broken frame

[heppstux]

FrameAware.apply_to_frames iterates range(self.im.n_frames) and calls self.im.seek(i) with no error handling.
I just stumbled over this while uploading JPGs from a DJI Drone to a django-cms project with filer. Seems they create MPO JPEGs, whose embedded preview frame have malformed offsets and make PIL raise ValueError("No data found for frame").

So a single bad secondary frame currently kills the entire thumbnail pipeline, even though the primary frame would render correctly.

Suggested Fix:

Tolerate per-frame failures and continue with whatever frames were successfully read (at minimum frame 0):

  def apply_to_frames(self, method, *args, **kwargs):                                                                                                                                                                  
      new_frames = []                                                                                                                                                                                                  
      for i in range(self.im.n_frames):
          try:                                                                                                                                                                                                         
              self.im.seek(i)                                                                                                                                                                                          
              new_frames.append(method(*args, **kwargs))
          except (ValueError, EOFError, OSError):                                                                                                                                                                      
              break                                                                                                                                                                                                    
      if not new_frames:
          self.im.seek(0)                                                                                                                                                                                              
          new_frames.append(method(*args, **kwargs))
      ...                                                                                                                                                                                                              

Behavior for valid multi-frame inputs (animated GIF/WebP) is unchanged; malformed MPOs degrade to a clean single-frame thumbnail instead of crashing.

[defgsus]

Hi @heppstux
i had the same issue and suggested to add a parameter to the processor to allow skipping faulty frames: #660 (comment)

I think to get forward, we need to create a good pull-request including a test-case with a bogus jpeg.
Cheers