img: add _App0Marker.horz_dpi and .vert_dpi

Steve Canny · Steve Canny · commit da83e15e3fcf · 2014-02-27T12:08:35.000-08:00
diff --git a/docx/image/jpeg.py b/docx/image/jpeg.py
@@ -280,6 +280,34 @@ def __init__(
         self._x_density = x_density
         self._y_density = y_density
 
+    @property
+    def horz_dpi(self):
+        """
+        Horizontal dots per inch specified in this marker, defaults to 72 if
+        not specified.
+        """
+        return self._dpi(self._x_density)
+
+    @property
+    def vert_dpi(self):
+        """
+        Vertical dots per inch specified in this marker, defaults to 72 if
+        not specified.
+        """
+        return self._dpi(self._y_density)
+
+    def _dpi(self, density):
+        """
+        Return dots per inch corresponding to *density* value.
+        """
+        if self._density_units == 1:
+            dpi = density
+        elif self._density_units == 2:
+            dpi = int(round(density * 2.54))
+        else:
+            dpi = 72
+        return dpi
+
     @classmethod
     def from_stream(cls, stream, marker_code, offset):
         """
diff --git a/tests/image/test_jpeg.py b/tests/image/test_jpeg.py
@@ -231,8 +231,31 @@ def it_can_construct_from_a_stream_and_offset(self, from_stream_fixture):
         )
         assert isinstance(app0_marker, _App0Marker)
 
+    def it_knows_the_image_dpi(self, dpi_fixture):
+        density_units, x_density, y_density, horz_dpi, vert_dpi = dpi_fixture
+        app0 = _App0Marker(
+            None, None, None, density_units, x_density, y_density
+        )
+        assert app0.horz_dpi == horz_dpi
+        assert app0.vert_dpi == vert_dpi
+
     # fixtures -------------------------------------------------------
 
+    @pytest.fixture
+    def _App0Marker__init_(self, request):
+        return initializer_mock(request, _App0Marker)
+
+    @pytest.fixture(params=[
+        (0, 100, 200,  72,  72),
+        (1, 100, 200, 100, 200),
+        (2, 100, 200, 254, 508),
+    ])
+    def dpi_fixture(self, request):
+        density_units, x_density, y_density, horz_dpi, vert_dpi = (
+            request.param
+        )
+        return density_units, x_density, y_density, horz_dpi, vert_dpi
+
     @pytest.fixture
     def from_stream_fixture(self, request, _App0Marker__init_):
         bytes_ = b'\x00\x10JFIF\x00\x01\x01\x01\x00\x2A\x00\x18'
@@ -244,10 +267,6 @@ def from_stream_fixture(self, request, _App0Marker__init_):
             density_units, x_density, y_density
         )
 
-    @pytest.fixture
-    def _App0Marker__init_(self, request):
-        return initializer_mock(request, _App0Marker)
-
 
 class Describe_SofMarker(object):
 
