img: add Jfif.from_stream()

Steve Canny · Steve Canny · commit 1e6d9bab7596 · 2014-02-27T12:08:34.000-08:00
diff --git a/docx/image/jpeg.py b/docx/image/jpeg.py
@@ -1,5 +1,10 @@
 # encoding: utf-8
 
+"""
+Objects related to parsing headers of JPEG image streams, both JFIF and Exif
+sub-formats.
+"""
+
 from __future__ import absolute_import, division, print_function
 
 from .image import Image
@@ -21,3 +26,63 @@ class Jfif(Jpeg):
     """
     Image header parser for JFIF image format
     """
+    def __init__(self, blob, filename, cx, cy, horz_dpi, vert_dpi):
+        super(Jfif, self).__init__(blob, filename, cx, cy, attrs={})
+        self._horz_dpi = horz_dpi
+        self._vert_dpi = vert_dpi
+
+    @classmethod
+    def from_stream(cls, stream, blob, filename):
+        """
+        Return a |Jfif| instance having header properties parsed from image
+        in *stream*.
+        """
+        markers = _JfifMarkers.from_stream(stream)
+        sof, app0 = markers.sof, markers.app0
+        cx, cy = sof.px_width, sof.px_height
+        horz_dpi, vert_dpi = app0.horz_dpi, app0.vert_dpi
+        return cls(blob, filename, cx, cy, horz_dpi, vert_dpi)
+
+    @property
+    def horz_dpi(self):
+        """
+        Integer dots per inch for the width of this image. Defaults to 72
+        when not present in the file, as is often the case.
+        """
+        return self._horz_dpi
+
+    @property
+    def vert_dpi(self):
+        """
+        Integer dots per inch for the height of this image. Defaults to 72
+        when not present in the file, as is often the case.
+        """
+        return self._vert_dpi
+
+
+class _JfifMarkers(object):
+    """
+    Sequence of markers in a JPEG file, perhaps truncated at first SOS marker
+    for performance reasons.
+    """
+    @classmethod
+    def from_stream(cls, stream):
+        """
+        Return a |_JfifMarkers| instance containing a |_JfifMarker| instance
+        for each marker in *stream*.
+        """
+        raise NotImplementedError
+
+    @property
+    def app0(self):
+        """
+        First APP0 marker in image markers.
+        """
+        raise NotImplementedError
+
+    @property
+    def sof(self):
+        """
+        First start of frame (SOFn) marker in this sequence.
+        """
+        raise NotImplementedError
diff --git a/tests/image/test_jpeg.py b/tests/image/test_jpeg.py
@@ -0,0 +1,69 @@
+# encoding: utf-8
+
+"""
+Test suite for docx.image.jpeg module
+"""
+
+from __future__ import absolute_import, print_function
+
+import pytest
+
+from docx.compat import BytesIO
+from docx.image.jpeg import Jfif, _JfifMarkers
+
+from ..unitutil import class_mock, instance_mock
+
+
+class DescribeJfif(object):
+
+    def it_can_construct_from_a_jfif_stream(self, from_stream_fixture):
+        # fixture ----------------------
+        (stream_, blob_, filename_, _JfifMarkers_, px_width, px_height,
+         horz_dpi, vert_dpi) = from_stream_fixture
+        # exercise ---------------------
+        jfif = Jfif.from_stream(stream_, blob_, filename_)
+        # verify -----------------------
+        _JfifMarkers_.from_stream.assert_called_once_with(stream_)
+        assert isinstance(jfif, Jfif)
+        assert jfif.px_width == px_width
+        assert jfif.px_height == px_height
+        assert jfif.horz_dpi == horz_dpi
+        assert jfif.vert_dpi == vert_dpi
+
+    # 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_, _JfifMarkers_, jfif_markers_):
+        px_width, px_height = 111, 222
+        horz_dpi, vert_dpi = 333, 444
+        jfif_markers_.sof.px_width = px_width
+        jfif_markers_.sof.px_height = px_height
+        jfif_markers_.app0.horz_dpi = horz_dpi
+        jfif_markers_.app0.vert_dpi = vert_dpi
+        return (
+            stream_, blob_, filename_, _JfifMarkers_, px_width, px_height,
+            horz_dpi, vert_dpi
+        )
+
+    @pytest.fixture
+    def _JfifMarkers_(self, request, jfif_markers_):
+        _JfifMarkers_ = class_mock(request, 'docx.image.jpeg._JfifMarkers')
+        _JfifMarkers_.from_stream.return_value = jfif_markers_
+        return _JfifMarkers_
+
+    @pytest.fixture
+    def jfif_markers_(self, request):
+        return instance_mock(request, _JfifMarkers)
+
+    @pytest.fixture
+    def stream_(self, request):
+        return instance_mock(request, BytesIO)
