img: add Tiff.from_stream()

Steve Canny · Steve Canny · commit fadb89dd2dea · 2014-02-27T12:08:35.000-08:00
diff --git a/docx/image/tiff.py b/docx/image/tiff.py
@@ -10,3 +10,65 @@ class Tiff(Image):
     Image header parser for TIFF images. Handles both big and little endian
     byte ordering.
     """
+    @classmethod
+    def from_stream(cls, stream, blob, filename):
+        """
+        Return a |Tiff| instance containing the properties of the TIFF image
+        in *stream*.
+        """
+        parser = _TiffParser.parse(stream)
+        px_width = parser.px_width
+        px_height = parser.px_height
+        horz_dpi = parser.horz_dpi
+        vert_dpi = parser.vert_dpi
+        return cls(blob, filename, px_width, px_height, horz_dpi, vert_dpi)
+
+
+class _TiffParser(object):
+    """
+    Parses a TIFF image stream to extract the image properties found in its
+    main image file directory (IFD)
+    """
+    @classmethod
+    def parse(cls, stream):
+        """
+        Return an instance of |_TiffParser| containing the properties parsed
+        from the TIFF image in *stream*.
+        """
+        raise NotImplementedError
+
+    @property
+    def horz_dpi(self):
+        """
+        The horizontal dots per inch value calculated from the XResolution
+        and ResolutionUnit tags of the IFD; defaults to 72 if those tags are
+        not present.
+        """
+        raise NotImplementedError
+
+    @property
+    def px_height(self):
+        """
+        The number of stacked rows of pixels in the image, |None| if the IFD
+        contains no ``ImageLength`` tag, the expected case when the TIFF is
+        embeded in an Exif image.
+        """
+        raise NotImplementedError
+
+    @property
+    def px_width(self):
+        """
+        The number of pixels in each row in the image, |None| if the IFD
+        contains no ``ImageWidth`` tag, the expected case when the TIFF is
+        embeded in an Exif image.
+        """
+        raise NotImplementedError
+
+    @property
+    def vert_dpi(self):
+        """
+        The vertical dots per inch value calculated from the XResolution and
+        ResolutionUnit tags of the IFD; defaults to 72 if those tags are not
+        present.
+        """
+        raise NotImplementedError
diff --git a/tests/image/test_tiff.py b/tests/image/test_tiff.py
@@ -0,0 +1,70 @@
+# encoding: utf-8
+
+"""
+Test suite for docx.image.tiff module
+"""
+
+from __future__ import absolute_import, print_function
+
+import pytest
+
+from docx.compat import BytesIO
+from docx.image.tiff import Tiff, _TiffParser
+
+from ..unitutil import class_mock, initializer_mock, instance_mock
+
+
+class DescribeTiff(object):
+
+    def it_can_construct_from_a_tiff_stream(self, from_stream_fixture):
+        (stream_, blob_, filename_, _TiffParser_, Tiff__init_, px_width,
+         px_height, horz_dpi, vert_dpi) = from_stream_fixture
+        tiff = Tiff.from_stream(stream_, blob_, filename_)
+        _TiffParser_.parse.assert_called_once_with(stream_)
+        Tiff__init_.assert_called_once_with(
+            blob_, filename_, px_width, px_height, horz_dpi, vert_dpi
+        )
+        assert isinstance(tiff, Tiff)
+
+    # fixtures -------------------------------------------------------
+
+    @pytest.fixture
+    def blob_(self, request):
+        return instance_mock(request, bytes)
+
+    @pytest.fixture
+    def filename_(self, request):
+        return instance_mock(request, str)
+
+    @pytest.fixture
+    def from_stream_fixture(
+            self, stream_, blob_, filename_, _TiffParser_, tiff_parser_,
+            Tiff__init_):
+        px_width, px_height = 111, 222
+        horz_dpi, vert_dpi = 333, 444
+        tiff_parser_.px_width = px_width
+        tiff_parser_.px_height = px_height
+        tiff_parser_.horz_dpi = horz_dpi
+        tiff_parser_.vert_dpi = vert_dpi
+        return (
+            stream_, blob_, filename_, _TiffParser_, Tiff__init_, px_width,
+            px_height, horz_dpi, vert_dpi
+        )
+
+    @pytest.fixture
+    def Tiff__init_(self, request):
+        return initializer_mock(request, Tiff)
+
+    @pytest.fixture
+    def _TiffParser_(self, request, tiff_parser_):
+        _TiffParser_ = class_mock(request, 'docx.image.tiff._TiffParser')
+        _TiffParser_.parse.return_value = tiff_parser_
+        return _TiffParser_
+
+    @pytest.fixture
+    def tiff_parser_(self, request):
+        return instance_mock(request, _TiffParser)
+
+    @pytest.fixture
+    def stream_(self, request):
+        return instance_mock(request, BytesIO)
