img: add Jpeg formats to recognizer

Steve Canny · Steve Canny · commit 98f3f24ec34b · 2014-02-27T12:08:33.000-08:00
Along the way:

* move image_cls_that_can_parse(stream) import into the calling method
to avoid circular import
diff --git a/docx/image/__init__.py b/docx/image/__init__.py
@@ -19,14 +19,17 @@
 
 from docx.compat import BytesIO, is_string
 from docx.exceptions import UnrecognizedImageError
+from docx.image.jpeg import Exif, Jfif
 from docx.image.png import Png
 from docx.opc.constants import CONTENT_TYPE as CT
 from docx.shared import lazyproperty
 
 
 SIGNATURES = (
     # class, offset, signature_bytes
-    (Png, 0, b'\x89PNG\x0D\x0A\x1A\x0A'),
+    (Png,  0, b'\x89PNG\x0D\x0A\x1A\x0A'),
+    (Jfif, 6, b'JFIF'),
+    (Exif, 6, b'Exif'),
 )
 
 
diff --git a/docx/image/image.py b/docx/image/image.py
@@ -5,14 +5,11 @@
 size, as a required step in including them in a document.
 """
 
-from __future__ import (
-    absolute_import, division, print_function, unicode_literals
-)
+from __future__ import absolute_import, division, print_function
 
 import os
 
 from docx.compat import BytesIO, is_string
-from docx.image import image_cls_that_can_parse
 
 
 class Image(object):
@@ -45,5 +42,7 @@ def _from_stream(cls, stream, blob, filename=None):
         Return an instance of the |Image| subclass corresponding to the
         format of the image in *stream*.
         """
+        # import at execution time to avoid circular import
+        from docx.image import image_cls_that_can_parse
         ImageSubclass = image_cls_that_can_parse(stream)
         return ImageSubclass(stream, blob, filename)
diff --git a/docx/image/jpeg.py b/docx/image/jpeg.py
@@ -0,0 +1,23 @@
+# encoding: utf-8
+
+from __future__ import absolute_import, division, print_function
+
+from .image import Image
+
+
+class Jpeg(Image):
+    """
+    Base class for JFIF and EXIF subclasses.
+    """
+
+
+class Exif(Jpeg):
+    """
+    Image header parser for Exif image format
+    """
+
+
+class Jfif(Jpeg):
+    """
+    Image header parser for JFIF image format
+    """
diff --git a/docx/image/png.py b/docx/image/png.py
@@ -2,8 +2,10 @@
 
 from __future__ import absolute_import, division, print_function
 
+from .image import Image
 
-class Png(object):
+
+class Png(Image):
     """
     Image header parser for PNG images
     """
diff --git a/tests/image/test_image.py b/tests/image/test_image.py
@@ -12,6 +12,7 @@
 from docx.exceptions import UnrecognizedImageError
 from docx.image import image_cls_that_can_parse, Image_OLD
 from docx.image.image import Image
+from docx.image.jpeg import Exif, Jfif
 from docx.image.png import Png
 from docx.opc.constants import CONTENT_TYPE as CT
 
@@ -36,7 +37,9 @@ def it_raises_on_unrecognized_image_stream(self):
     # fixtures -------------------------------------------------------
 
     @pytest.fixture(params=[
-        ('python-icon.png', Png),
+        ('python-icon.png',  Png),
+        ('python-icon.jpeg', Jfif),
+        ('exif-420-dpi.jpg', Exif),
     ])
     def image_cls_lookup_fixture(self, request):
         image_filename, expected_class = request.param
@@ -130,7 +133,7 @@ def image_cls_(self, request, image_):
     @pytest.fixture
     def image_cls_that_can_parse_(self, request, image_cls_):
         return function_mock(
-            request, 'docx.image.image.image_cls_that_can_parse',
+            request, 'docx.image.image_cls_that_can_parse',
             return_value=image_cls_
         )
 
diff --git a/tests/test_files/exif-420-dpi.jpg b/tests/test_files/exif-420-dpi.jpg
diff --git a/tests/test_files/jfif-iguana.jpg b/tests/test_files/jfif-iguana.jpg
