Fixed #23103 -- Annotated ImageField file with image and content_type attributes.

Thanks Jeremy Dunck for the suggestion and Nick Sanford for review.

django/forms/fields.py

@@ -659,8 +659,13 @@ class ImageField(FileField):
         try:
             # load() could spot a truncated JPEG, but it loads the entire
             # image in memory, which is a DoS vector. See #3848 and #18520.
+            image = Image.open(file)
             # verify() must be called immediately after the constructor.
-            Image.open(file).verify()
+            image.verify()
+
+            # Annotating so subclasses can reuse it for their own validation
+            f.image = image
+            f.content_type = Image.MIME[image.format]
         except Exception:
             # Pillow doesn't recognize it as an image.
             six.reraise(ValidationError, ValidationError(

docs/ref/forms/fields.txt

@@ -649,7 +649,16 @@ For each field, we describe the default widget used if you don't specify
     When you use an ``ImageField`` on a form, you must also remember to
     :ref:`bind the file data to the form <binding-uploaded-files>`.
 
+    .. versionchanged:: 1.8
+
+        After the field has been cleaned and validated, the ``UploadedFile``
+        object will have an additional ``image`` attribute containing the Pillow
+        `Image`_ instance used to check if the file was a valid image.
+        ``UploadedFile.content_type`` is also updated with the image's content
+        type as determined by Pillow.
+
 .. _Pillow: http://pillow.readthedocs.org/en/latest/
+.. _Image: https://pillow.readthedocs.org/en/latest/reference/Image.html
 
 ``IntegerField``
 ~~~~~~~~~~~~~~~~

docs/releases/1.8.txt

@@ -160,6 +160,12 @@ Forms
   :attr:`~django.forms.extras.widgets.SelectDateWidget.empty_label` argument, which will
   override the top list choice label when :class:`~django.forms.DateField` is not required.
 
+* After an :class:`~django.forms.ImageField` has been cleaned and validated, the
+  ``UploadedFile`` object will have an additional ``image`` attribute containing
+  the Pillow ``Image`` instance used to check if the file was a valid image. It
+  will also update ``UploadedFile.content_type`` with the image's content type
+  as determined by Pillow.
+
 Internationalization
 ^^^^^^^^^^^^^^^^^^^^
 

tests/forms_tests/tests/test_fields.py

@@ -31,12 +31,18 @@ import pickle
 import re
 import os
 from decimal import Decimal
+from unittest import skipIf
+
+try:
+    from PIL import Image
+except ImportError:
+    Image = None
 
 from django.core.files.uploadedfile import SimpleUploadedFile
 from django.forms import (
     BooleanField, CharField, ChoiceField, ComboField, DateField, DateTimeField,
     DecimalField, EmailField, Field, FileField, FilePathField, FloatField,
-    Form, forms, HiddenInput, IntegerField, MultipleChoiceField,
+    Form, forms, HiddenInput, ImageField, IntegerField, MultipleChoiceField,
     NullBooleanField, NumberInput, PasswordInput, RadioSelect, RegexField,
     SplitDateTimeField, TextInput, Textarea, TimeField, TypedChoiceField,
     TypedMultipleChoiceField, URLField, ValidationError, Widget,
@@ -741,6 +747,24 @@ class FieldsTests(SimpleTestCase):
         # with here)
         self.assertTrue(f._has_changed('resume.txt', {'filename': 'resume.txt', 'content': 'My resume'}))
 
+    # ImageField ##################################################################
+
+    @skipIf(Image is None, "Pillow is required to test ImageField")
+    def test_imagefield_annotate_with_image_after_clean(self):
+        f = ImageField()
+
+        img_path = os.path.dirname(upath(__file__)) + '/filepath_test_files/1x1.png'
+        with open(img_path, 'rb') as img_file:
+            img_data = img_file.read()
+
+        img_file = SimpleUploadedFile('1x1.png', img_data)
+        img_file.content_type = 'text/plain'
+
+        uploaded_file = f.clean(img_file)
+
+        self.assertEqual('PNG', uploaded_file.image.format)
+        self.assertEqual('image/png', uploaded_file.content_type)
+
     # URLField ##################################################################
 
     def test_urlfield_1(self):
@@ -1262,6 +1286,7 @@ class FieldsTests(SimpleTestCase):
         f.choices.sort()
         expected = [
             ('/tests/forms_tests/tests/filepath_test_files/.dot-file', '.dot-file'),
+            ('/tests/forms_tests/tests/filepath_test_files/1x1.png', '1x1.png'),
             ('/tests/forms_tests/tests/filepath_test_files/directory', 'directory'),
             ('/tests/forms_tests/tests/filepath_test_files/fake-image.jpg', 'fake-image.jpg'),
             ('/tests/forms_tests/tests/filepath_test_files/real-text-file.txt', 'real-text-file.txt'),