July 3, 2011
Installed Fedora 15

Despite all the efforts to make Fedora 15 easier and more user friendly, making power users kind of unhappy by removing functionality and features, it doesn’t look ready yet (please, remove more features! :D).

I installed Fedora 15 and it’s running in Gnome fall back mode (no hw acceleration here, so it’s OK). First thing I tried was updating my system: Applications > System Tools > Software Update; and it didn’t work. The error about a failing transaction was quite cryptic to me, and I didn’t know how to fix it (I tried to update several times but it didn’t work).

Running yum from a console works as expected, though. Fortunately nobody thought that yum had to be removed because some weird reason!

This is my first experience with Gnome fall back mode, and it feels less crippled than the regular Gnome interface. Too bad the drag-to-maximize thing doesn’t work in fall back mode.

by jjm on 9:55am  |   URL: http://tmblr.co/ZPorZy6iMkTC
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(Notes: 3)
  
Filed under: Gnome Fedora Software Update yum Fedora 15 Fall back mode Error FAIL 
April 30, 2011
PIL Error Saving a JPEG Image

This bug has been very difficult to identify and workaround, so I’m writing this post for the record.

When I tried to save a JPEG encoded image using optimize option, I was getting the following error with some images:

Traceback (most recent call last):

  File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/base.py", line 100, in get_response
    response = callback(request, *callback_args, **callback_kwargs)

  File "/home/motivator/../motivator/public/views.py", line 227, in creator_done_view
    img.copy().resize((480, 480*h/w), Image.ANTIALIAS).save(fd, 'JPEG', optimize=True)

  File "/usr/lib/python2.6/dist-packages/PIL/Image.py", line 1439, in save
    save_handler(self, fp, filename)

  File "/usr/lib/python2.6/dist-packages/PIL/JpegImagePlugin.py", line 471, in _save
    ImageFile._save(im, fp, [("jpeg", (0,0)+im.size, 0, rawmode)])

  File "/usr/lib/python2.6/dist-packages/PIL/ImageFile.py", line 501, in _save
    raise IOError("encoder error %d when writing image file" % s)

IOError: encoder error -2 when writing image file

The weird thing is that it was happening with a couple of images, and I couldn’t find a pattern (although the image size seemed to be relevant).

The problem looks related to libjpeg (the library PIL is using) and the way PIL is encoding the JPEG, and after trying blindly to tweak the saving process, I managed to get it to work setting ImageFile.MAXBLOCK to a big value (by default it’s using 64KB).

 # before saving, increase MAXBLOCK
from PIL import ImageFile
    ImageFile.MAXBLOCK = 1024*1024

I don’t know what block size works best, because I certainly don’t know what kind of image is making PIL to crash, but 1MB it’s been working fine for me so far.

When I was looking for information about this bug I’ve found that there’s some people not very happy with PIL because of the JPEG support. It’s working OK for me now, but I’m not 100% happy with the workaround.

by jjm on 7:21pm  |   URL: http://tmblr.co/ZPorZy4kYDG-
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(Notes: 3)
  
Filed under: Python PIL Python Image Library save crash libjpeg JPEG error workaround