img: add _PngParser.px_width and .px_height

Steve Canny · Steve Canny · commit 70e09486257f · 2014-03-01T01:35:30.000-08:00
diff --git a/docx/image/png.py b/docx/image/png.py
@@ -167,6 +167,10 @@ class _PngParser(object):
     Parses a PNG image stream to extract the image properties found in its
     chunks.
     """
+    def __init__(self, chunks):
+        super(_PngParser, self).__init__()
+        self._chunks = chunks
+
     @classmethod
     def parse(cls, stream):
         """
@@ -181,14 +185,16 @@ def px_width(self):
         """
         The number of pixels in each row of the image.
         """
-        raise NotImplementedError
+        IHDR = self._chunks.IHDR
+        return IHDR.px_width
 
     @property
     def px_height(self):
         """
         The number of stacked rows of pixels in the image.
         """
-        raise NotImplementedError
+        IHDR = self._chunks.IHDR
+        return IHDR.px_height
 
     @property
     def horz_dpi(self):
@@ -211,6 +217,10 @@ class _Chunks(object):
     """
     Collection of the chunks parsed from a PNG image stream
     """
+    def __init__(self, chunk_lst):
+        super(_Chunks, self).__init__()
+        self._chunks = chunk_lst
+
     @classmethod
     def from_stream(cls, stream):
         """
@@ -220,6 +230,13 @@ def from_stream(cls, stream):
         chunk_lst = [chunk for chunk in chunk_parser.iter_chunks()]
         return cls(chunk_lst)
 
+    @property
+    def IHDR(self):
+        """
+        IHDR chunk in PNG image
+        """
+        raise NotImplementedError
+
 
 class _ChunkParser(object):
     """
diff --git a/tests/image/test_png.py b/tests/image/test_png.py
@@ -266,6 +266,11 @@ def it_can_parse_the_headers_of_a_PNG_stream(self, parse_fixture):
         _PngParser__init_.assert_called_once_with(chunks_)
         assert isinstance(png_parser, _PngParser)
 
+    def it_knows_the_image_width_and_height(self, dimensions_fixture):
+        png_parser, px_width, px_height = dimensions_fixture
+        assert png_parser.px_width == px_width
+        assert png_parser.px_height == px_height
+
     # fixtures -------------------------------------------------------
 
     @pytest.fixture
@@ -278,6 +283,14 @@ def _Chunks_(self, request, chunks_):
     def chunks_(self, request):
         return instance_mock(request, _Chunks)
 
+    @pytest.fixture
+    def dimensions_fixture(self, chunks_):
+        px_width, px_height = 12, 34
+        chunks_.IHDR.px_width = px_width
+        chunks_.IHDR.px_height = px_height
+        png_parser = _PngParser(chunks_)
+        return png_parser, px_width, px_height
+
     @pytest.fixture
     def parse_fixture(self, stream_, _Chunks_, _PngParser__init_, chunks_):
         return stream_, _Chunks_, _PngParser__init_, chunks_
