[Image-SIG] why does Image.open fail after reload(Image) -- fixable bug ??

[Sebastian Haase]

On Mon, Apr 14, 2008 at 11:27 AM, Sebastian Haase <haase at msg.ucsf.edu> wrote:
> Hi,
>
>  this is a short question:
>
>  Why does Image.open fail after reload(Image) ?
>
>  Here is what I get :
>  {{{
>  >>> import Image
>  >>> i = Image.open(r"/Users/labuser/Desktop/Picture 5.png")
>  >>> i.size
>  (1920, 1200)
>  >>> reload(Image)
>  <module 'Image' from '....../PIL/Image.pyc'>
>  >>> i = Image.open("Picture 5.png")
>  Traceback (most recent call last):
>   File "<input>", line 1, in <module>
>   File "......./PIL/Image.py", line 1916, in open
>     raise IOError("cannot identify image file")
>  IOError: cannot identify image file
>  >>> Image.VERSION
>  '1.1.6'
>  }}}
>
>  Since I ran into this a couple times,
>  I was just wondering if this could be fixed ?
>
>  Thanks for PIL,
>  Sebastian Haase
>

It appears that in Image.py
there are two functions named preinit() and init().
While preinit() seems harmless ,
I found that init() calls
__import__(f, globals(), locals(), [])
with f being every files found ending in "ImagePlugin.py" (without the '.py')

I guess that these calls are supposed to fill in the dictionaries
OPEN, SAVE and ID (and more).
But __import__ does nothing when called the second time for a given
file (import is no reload).
So they stay empty.

Any idea ho to fix this ?
How about changing these lines

_initialized = 0
ID = []
OPEN = {}
MIME = {}
SAVE = {}
EXTENSION = {}

into

try:
   _initialied  # check if we are imported and not reloaded
except:
   _initialized = 0
   ID = []
   OPEN = {}
   MIME = {}
   SAVE = {}
   EXTENSION = {}

Cheers,
Sebastian Haase