img: add ImagePart cx, cy from loaded part

Steve Canny · Steve Canny · commit 994b290f2d13 · 2013-12-29T23:21:19.000-08:00
Along the way:

* add Image.from_blob() constructor
* add ImagePart.image lazyproperty
diff --git a/docx/parts/image.py b/docx/parts/image.py
@@ -16,6 +16,8 @@
 except ImportError:
     import Image as PIL_Image
 
+from StringIO import StringIO
+
 from docx.opc.constants import CONTENT_TYPE as CT
 from docx.opc.package import Part
 from docx.shared import Emu, Inches, lazyproperty
@@ -68,6 +70,19 @@ def filename(self):
         """
         return self._filename
 
+    @classmethod
+    def from_blob(cls, blob):
+        stream = StringIO(blob)
+        content_type, px_width, px_height, horz_dpi, vert_dpi = (
+            cls._analyze_image(stream)
+        )
+        stream.close()
+        filename = 'image%s' % cls._def_mime_ext(content_type)
+        return cls(
+            blob, filename, content_type, px_width, px_height, horz_dpi,
+            vert_dpi
+        )
+
     @property
     def horz_dpi(self):
         """
@@ -208,8 +223,8 @@ def default_cx(self):
         Native width of this image, calculated from its width in pixels and
         horizontal dots per inch (dpi).
         """
-        px_width = self._image.px_width
-        horz_dpi = self._image.horz_dpi
+        px_width = self.image.px_width
+        horz_dpi = self.image.horz_dpi
         width_in_inches = px_width / horz_dpi
         return Inches(width_in_inches)
 
@@ -219,8 +234,8 @@ def default_cy(self):
         Native height of this image, calculated from its height in pixels and
         vertical dots per inch (dpi).
         """
-        px_height = self._image.px_height
-        horz_dpi = self._image.horz_dpi
+        px_height = self.image.px_height
+        horz_dpi = self.image.horz_dpi
         height_in_emu = 914400 * px_height / horz_dpi
         return Emu(height_in_emu)
 
@@ -243,6 +258,12 @@ def from_image(cls, image, partname):
         """
         return ImagePart(partname, image.content_type, image.blob, image)
 
+    @property
+    def image(self):
+        if self._image is None:
+            self._image = Image.from_blob(self.blob)
+        return self._image
+
     @classmethod
     def load(cls, partname, content_type, blob, package):
         """
diff --git a/tests/parts/test_image.py b/tests/parts/test_image.py
@@ -118,15 +118,24 @@ def it_knows_its_default_dimensions_in_EMU(self, dimensions_fixture):
     def blob_(self, request):
         return instance_mock(request, str)
 
-    # param for one known from test_files at 72 dpi and created with from_image
-    # param for one loaded by PartFactory with no Image instance
-    @pytest.fixture
-    def dimensions_fixture(self):
+    @pytest.fixture(params=['loaded', 'new'])
+    def dimensions_fixture(self, request):
         image_file_path = test_file('monty-truth.png')
         image = Image.load(image_file_path)
-        image_part = ImagePart.from_image(image, None)
-        cx, cy = 1905000, 2717800
-        return image_part, cx, cy
+        expected_cx, expected_cy = 1905000, 2717800
+
+        # case 1: image part is loaded by PartFactory w/no Image inst
+        if request.param == 'loaded':
+            partname = PackURI('/word/media/image1.png')
+            content_type = CT.PNG
+            image_part = ImagePart.load(
+                partname, content_type, image.blob, None
+            )
+        # case 2: image part is newly created from image file
+        elif request.param == 'new':
+            image_part = ImagePart.from_image(image, None)
+
+        return image_part, expected_cx, expected_cy
 
     @pytest.fixture
     def from_image_fixture(self, image_, partname_, ImagePart__init__):
