img: add GIF support

Steve Canny · Steve Canny · commit 9a2296ea9baa · 2014-03-01T01:35:29.000-08:00
diff --git a/docx/image/constants.py b/docx/image/constants.py
@@ -97,6 +97,7 @@ class MIME_TYPE(object):
     """
     Image content types
     """
+    GIF = 'image/gif'
     JPEG = 'image/jpeg'
     PNG = 'image/png'
     TIFF = 'image/tiff'
diff --git a/docx/image/gif.py b/docx/image/gif.py
@@ -2,6 +2,9 @@
 
 from __future__ import absolute_import, division, print_function
 
+from struct import Struct
+
+from .constants import MIME_TYPE
 from .image import BaseImageHeader
 
 
@@ -17,4 +20,21 @@ def from_stream(cls, stream):
         Return |Gif| instance having header properties parsed from GIF image
         in *stream*.
         """
-        return cls(None, None, None, None)
+        px_width, px_height = cls._dimensions_from_stream(stream)
+        return cls(px_width, px_height, 72, 72)
+
+    @property
+    def content_type(self):
+        """
+        MIME content type for this image, unconditionally `image/png` for
+        PNG images.
+        """
+        return MIME_TYPE.GIF
+
+    @classmethod
+    def _dimensions_from_stream(cls, stream):
+        stream.seek(6)
+        bytes_ = stream.read(4)
+        struct = Struct('<HH')
+        px_width, px_height = struct.unpack(bytes_)
+        return px_width, px_height
diff --git a/features/img-characterize-image.feature b/features/img-characterize-image.feature
@@ -22,3 +22,4 @@ Feature: Characterize an image file
      | sample.tif       | image/tiff | 1600 | 2100 |   200    |   200    |
      | jpeg420exif.jpg  | image/jpeg | 2048 | 1536 |    72    |    72    |
      | court-exif.jpg   | image/jpeg |  500 |  375 |   256    |   256    |
+     | lena.gif         | image/gif  |  256 |  256 |    72    |    72    |
diff --git a/features/steps/test_files/lena.gif b/features/steps/test_files/lena.gif
diff --git a/tests/image/test_gif.py b/tests/image/test_gif.py
@@ -0,0 +1,41 @@
+# encoding: utf-8
+
+"""
+Test suite for docx.image.gif module
+"""
+
+from __future__ import absolute_import, print_function
+
+import pytest
+
+from docx.compat import BytesIO
+from docx.image.constants import MIME_TYPE
+from docx.image.gif import Gif
+
+from ..unitutil import initializer_mock
+
+
+class DescribeGif(object):
+
+    def it_can_construct_from_a_gif_stream(self, from_stream_fixture):
+        stream, Gif__init__, cx, cy = from_stream_fixture
+        gif = Gif.from_stream(stream)
+        Gif__init__.assert_called_once_with(cx, cy, 72, 72)
+        assert isinstance(gif, Gif)
+
+    def it_knows_its_content_type(self):
+        gif = Gif(None, None, None, None)
+        assert gif.content_type == MIME_TYPE.GIF
+
+    # fixtures -------------------------------------------------------
+
+    @pytest.fixture
+    def from_stream_fixture(self, Gif__init__):
+        cx, cy = 42, 24
+        bytes_ = b'filler\x2A\x00\x18\x00'
+        stream = BytesIO(bytes_)
+        return stream, Gif__init__, cx, cy
+
+    @pytest.fixture
+    def Gif__init__(self, request):
+        return initializer_mock(request, Gif)
