Change how we set ImageFile.MAXBLOCK

Previously, we set it to an arbitrary large number (which turned out
not to be large enough in some cases). Since we may have been
overriding something the user explicitly chose (and our value may be
overridden by another app), that probably wasn't good. After this
change, `MAXBLOCK` is only increased when it needs to be--and even
then, only temporarily.

imagekit/models.py

@@ -2,22 +2,17 @@ import os
 import datetime
 from StringIO import StringIO
 
-from django.conf import settings
 from django.core.files.base import ContentFile
 from django.db import models
 from django.db.models.fields.files import ImageFieldFile
 from django.db.models.signals import post_save, post_delete
 from django.utils.encoding import force_unicode, smart_str
 
-from imagekit.lib import Image, ImageFile
 from imagekit.utils import img_to_fobj, get_spec_files, open_image, \
         format_to_extension, extension_to_format, UnknownFormatError, \
         UnknownExtensionError
 from imagekit.processors import ProcessorPipeline
 
-# Modify image file buffer size.
-ImageFile.MAXBLOCK = getattr(settings, 'PIL_IMAGEFILE_MAXBLOCK', 256 * 2 ** 10)
-
 
 class _ImageSpecMixin(object):
     def __init__(self, processors=None, quality=70, format=None):

imagekit/utils.py

@@ -21,10 +21,15 @@ def img_to_fobj(img, format, **kwargs):
     try:
         img.save(tmp, format, **kwargs)
     except IOError:
+        # PIL can have problems saving large JPEGs if MAXBLOCK isn't big enough,
+        # So if we have a problem saving, we temporarily increase it. See
+        # http://github.com/jdriscoll/django-imagekit/issues/50
         old_maxblock = ImageFile.MAXBLOCK
         ImageFile.MAXBLOCK = img.size[0] * img.size[1]
-        img.save(tmp, format, **kwargs)
-        ImageFile.MAXBLOCK = old_maxblock
+        try:
+            img.save(tmp, format, **kwargs)
+        finally:
+            ImageFile.MAXBLOCK = old_maxblock
     tmp.seek(0)
     return tmp