img: add BMP support

Steve Canny · Steve Canny · commit dd8c7efab4fc · 2014-03-01T01:35:29.000-08:00
diff --git a/docx/image/bmp.py b/docx/image/bmp.py
@@ -2,6 +2,8 @@
 
 from __future__ import absolute_import, division, print_function
 
+from .constants import MIME_TYPE
+from .helpers import LITTLE_ENDIAN, StreamReader
 from .image import BaseImageHeader
 
 
@@ -12,7 +14,36 @@ class Bmp(BaseImageHeader):
     @classmethod
     def from_stream(cls, stream):
         """
-        Return |Bmp| instance having header properties parsed from BMP image
-        in *stream*.
+        Return |Bmp| instance having header properties parsed from the BMP
+        image in *stream*.
         """
-        return cls(None, None, None, None)
+        stream_rdr = StreamReader(stream, LITTLE_ENDIAN)
+
+        px_width = stream_rdr.read_long(0x12)
+        px_height = stream_rdr.read_long(0x16)
+
+        horz_px_per_meter = stream_rdr.read_long(0x26)
+        vert_px_per_meter = stream_rdr.read_long(0x2A)
+
+        horz_dpi = cls._dpi(horz_px_per_meter)
+        vert_dpi = cls._dpi(vert_px_per_meter)
+
+        return cls(px_width, px_height, horz_dpi, vert_dpi)
+
+    @property
+    def content_type(self):
+        """
+        MIME content type for this image, unconditionally `image/bmp` for
+        BMP images.
+        """
+        return MIME_TYPE.BMP
+
+    @staticmethod
+    def _dpi(px_per_meter):
+        """
+        Return the integer pixels per inch from *px_per_meter*, defaulting to
+        96 if *px_per_meter* is zero.
+        """
+        if px_per_meter == 0:
+            return 96
+        return int(round(px_per_meter * 0.0254))
diff --git a/docx/image/constants.py b/docx/image/constants.py
@@ -97,6 +97,7 @@ class MIME_TYPE(object):
     """
     Image content types
     """
+    BMP = 'image/bmp'
     GIF = 'image/gif'
     JPEG = 'image/jpeg'
     PNG = 'image/png'
diff --git a/docx/image/gif.py b/docx/image/gif.py
@@ -26,8 +26,8 @@ def from_stream(cls, stream):
     @property
     def content_type(self):
         """
-        MIME content type for this image, unconditionally `image/png` for
-        PNG images.
+        MIME content type for this image, unconditionally `image/gif` for
+        GIF images.
         """
         return MIME_TYPE.GIF
 
diff --git a/docx/image/image.py b/docx/image/image.py
@@ -126,10 +126,11 @@ def content_type(self):
         """
         Abstract property definition, must be implemented by all subclasses.
         """
-        raise NotImplementedError(
+        msg = (
             'content_type property must be implemented by all subclasses of '
             'BaseImageHeader'
         )
+        raise NotImplementedError(msg)
 
     @property
     def px_width(self):
diff --git a/features/img-characterize-image.feature b/features/img-characterize-image.feature
@@ -23,3 +23,5 @@ Feature: Characterize an image file
      | jpeg420exif.jpg  | image/jpeg | 2048 | 1536 |    72    |    72    |
      | court-exif.jpg   | image/jpeg |  500 |  375 |   256    |   256    |
      | lena.gif         | image/gif  |  256 |  256 |    72    |    72    |
+     | lena.bmp         | image/bmp  |  512 |  512 |    96    |    96    |
+     | mountain.bmp     | image/bmp  |  640 |  480 |   300    |   300    |
diff --git a/features/steps/test_files/lena.bmp b/features/steps/test_files/lena.bmp
diff --git a/features/steps/test_files/mountain.bmp b/features/steps/test_files/mountain.bmp
diff --git a/tests/image/test_bmp.py b/tests/image/test_bmp.py
@@ -0,0 +1,44 @@
+# encoding: utf-8
+
+"""
+Test suite for docx.image.bmp module
+"""
+
+from __future__ import absolute_import, print_function
+
+import pytest
+
+from docx.compat import BytesIO
+from docx.image.constants import MIME_TYPE
+from docx.image.bmp import Bmp
+
+from ..unitutil import initializer_mock
+
+
+class DescribeBmp(object):
+
+    def it_can_construct_from_a_bmp_stream(self, from_stream_fixture):
+        stream, Bmp__init__, cx, cy, horz_dpi, vert_dpi = from_stream_fixture
+        bmp = Bmp.from_stream(stream)
+        Bmp__init__.assert_called_once_with(cx, cy, horz_dpi, vert_dpi)
+        assert isinstance(bmp, Bmp)
+
+    def it_knows_its_content_type(self):
+        bmp = Bmp(None, None, None, None)
+        assert bmp.content_type == MIME_TYPE.BMP
+
+    # fixtures -------------------------------------------------------
+
+    @pytest.fixture
+    def from_stream_fixture(self, Bmp__init__):
+        cx, cy, horz_dpi, vert_dpi = 26, 43, 200, 96
+        bytes_ = (
+            b'fillerfillerfiller\x1A\x00\x00\x00\x2B\x00\x00\x00'
+            b'fillerfiller\xB8\x1E\x00\x00\x00\x00\x00\x00'
+        )
+        stream = BytesIO(bytes_)
+        return stream, Bmp__init__, cx, cy, horz_dpi, vert_dpi
+
+    @pytest.fixture
+    def Bmp__init__(self, request):
+        return initializer_mock(request, Bmp)
