img: add _App1Marker._tiff_from_exif_segment()

Steve Canny · Steve Canny · commit 35cb7831a999 · 2014-03-01T01:35:29.000-08:00
diff --git a/docx/image/jpeg.py b/docx/image/jpeg.py
@@ -7,9 +7,11 @@
 
 from __future__ import absolute_import, division, print_function
 
+from ..compat import BytesIO
 from .constants import JPEG_MARKER_CODE, MIME_TYPE
 from .helpers import BIG_ENDIAN, StreamReader
 from .image import Image
+from .tiff import Tiff
 
 
 class Jpeg(Image):
@@ -436,7 +438,11 @@ def _tiff_from_exif_segment(cls, stream, offset, segment_length):
         Return a |Tiff| instance parsed from the Exif APP1 segment of
         *segment_length* at *offset* in *stream*.
         """
-        raise NotImplementedError
+        # wrap full segment in its own stream and feed to Tiff()
+        stream.seek(offset+8)
+        segment_bytes = stream.read(segment_length-8)
+        substream = BytesIO(segment_bytes)
+        return Tiff.from_stream(substream, None, None)
 
 
 class _SofMarker(_Marker):
diff --git a/tests/image/test_jpeg.py b/tests/image/test_jpeg.py
@@ -373,12 +373,28 @@ def it_can_construct_from_non_Exif_APP1_segment(self, non_Exif_fixture):
         )
         assert isinstance(app1_marker, _App1Marker)
 
+    def it_gets_a_tiff_from_its_Exif_segment_to_help_construct(
+            self, get_tiff_fixture):
+        stream, offset, length = get_tiff_fixture[:3]
+        BytesIO_, segment_bytes, substream_ = get_tiff_fixture[3:6]
+        Tiff_, tiff_ = get_tiff_fixture[6:]
+        tiff = _App1Marker._tiff_from_exif_segment(stream, offset, length)
+        BytesIO_.assert_called_once_with(segment_bytes)
+        Tiff_.from_stream.assert_called_once_with(substream_, None, None)
+        assert tiff is tiff_
+
     # fixtures -------------------------------------------------------
 
     @pytest.fixture
     def _App1Marker__init_(self, request):
         return initializer_mock(request, _App1Marker)
 
+    @pytest.fixture
+    def BytesIO_(self, request, substream_):
+        return class_mock(
+            request, 'docx.image.jpeg.BytesIO', return_value=substream_
+        )
+
     @pytest.fixture
     def from_stream_fixture(
             self, request, _App1Marker__init_, _tiff_from_exif_segment_):
@@ -391,13 +407,33 @@ def from_stream_fixture(
             _tiff_from_exif_segment_, horz_dpi, vert_dpi
         )
 
+    @pytest.fixture
+    def get_tiff_fixture(self, request, BytesIO_, substream_, Tiff_, tiff_):
+        bytes_ = b'xfillerxMM\x00*\x00\x00\x00\x42'
+        stream_reader = StreamReader(BytesIO(bytes_), BIG_ENDIAN)
+        offset, segment_length, segment_bytes = 0, 16, bytes_[8:]
+        return (
+            stream_reader, offset, segment_length, BytesIO_, segment_bytes,
+            substream_, Tiff_, tiff_
+        )
+
     @pytest.fixture
     def non_Exif_fixture(self, request, _App1Marker__init_):
         bytes_ = b'\x00\x42Foobar'
         stream_reader = StreamReader(BytesIO(bytes_), BIG_ENDIAN)
         marker_code, offset, length = JPEG_MARKER_CODE.APP1, 0, 66
         return stream_reader, marker_code, offset, _App1Marker__init_, length
 
+    @pytest.fixture
+    def substream_(self, request):
+        return instance_mock(request, BytesIO)
+
+    @pytest.fixture
+    def Tiff_(self, request, tiff_):
+        Tiff_ = class_mock(request, 'docx.image.jpeg.Tiff')
+        Tiff_.from_stream.return_value = tiff_
+        return Tiff_
+
     @pytest.fixture
     def tiff_(self, request):
         return instance_mock(request, Tiff, horz_dpi=42, vert_dpi=24)
