img: add _TiffParser.px_width and .px_height

Steve Canny · Steve Canny · commit cdb462d00fdd · 2014-02-27T12:08:36.000-08:00
diff --git a/docx/image/constants.py b/docx/image/constants.py
@@ -130,3 +130,40 @@ class TIFF_FLD_TYPE(object):
 
 
 TIFF_FLD = TIFF_FLD_TYPE
+
+
+class TIFF_TAG(object):
+    """
+    Tag codes for TIFF Image File Directory (IFD) entries.
+    """
+    IMAGE_WIDTH = 0x0100
+    IMAGE_LENGTH = 0x0101
+    X_RESOLUTION = 0x011A
+    Y_RESOLUTION = 0x011B
+    RESOLUTION_UNIT = 0x0128
+
+    tag_names = {
+        0x00FE: 'NewSubfileType',
+        0x0100: 'ImageWidth',
+        0x0101: 'ImageLength',
+        0x0102: 'BitsPerSample',
+        0x0103: 'Compression',
+        0x0106: 'PhotometricInterpretation',
+        0x010E: 'ImageDescription',
+        0x010F: 'Make',
+        0x0110: 'Model',
+        0x0111: 'StripOffsets',
+        0x0112: 'Orientation',
+        0x0115: 'SamplesPerPixel',
+        0x0117: 'StripByteCounts',
+        0x011A: 'XResolution',
+        0x011B: 'YResolution',
+        0x011C: 'PlanarConfiguration',
+        0x0128: 'ResolutionUnit',
+        0x0131: 'Software',
+        0x0132: 'DateTime',
+        0x0213: 'YCbCrPositioning',
+        0x8769: 'ExifTag',
+        0x8825: 'GPS IFD',
+        0xC4A5: 'PrintImageMatching',
+    }
diff --git a/docx/image/tiff.py b/docx/image/tiff.py
@@ -2,7 +2,7 @@
 
 from __future__ import absolute_import, division, print_function
 
-from .constants import TIFF_FLD
+from .constants import TIFF_FLD, TIFF_TAG
 from .helpers import BIG_ENDIAN, LITTLE_ENDIAN, StreamReader
 from .image import Image
 
@@ -31,9 +31,9 @@ class _TiffParser(object):
     Parses a TIFF image stream to extract the image properties found in its
     main image file directory (IFD)
     """
-    def __init__(self, ifd):
+    def __init__(self, ifd_entries):
         super(_TiffParser, self).__init__()
-        self._ifd = ifd
+        self._ifd_entries = ifd_entries
 
     @classmethod
     def parse(cls, stream):
@@ -62,7 +62,7 @@ def px_height(self):
         contains no ``ImageLength`` tag, the expected case when the TIFF is
         embeded in an Exif image.
         """
-        raise NotImplementedError
+        return self._ifd_entries.get(TIFF_TAG.IMAGE_LENGTH)
 
     @property
     def px_width(self):
@@ -71,7 +71,7 @@ def px_width(self):
         contains no ``ImageWidth`` tag, the expected case when the TIFF is
         embeded in an Exif image.
         """
-        raise NotImplementedError
+        return self._ifd_entries.get(TIFF_TAG.IMAGE_WIDTH)
 
     @property
     def vert_dpi(self):
@@ -108,6 +108,10 @@ class _IfdEntries(object):
     Image File Directory for a TIFF image, having mapping (dict) semantics
     allowing "tag" values to be retrieved by tag code.
     """
+    def __init__(self, entries):
+        super(_IfdEntries, self).__init__()
+        self._entries = entries
+
     @classmethod
     def from_stream(cls, stream, offset):
         """
@@ -118,6 +122,13 @@ def from_stream(cls, stream, offset):
         entries = dict((e.tag, e.value) for e in ifd_parser.iter_entries())
         return cls(entries)
 
+    def get(self, tag_code, default=None):
+        """
+        Return value of IFD entry having tag matching *tag_code*, or
+        *default* if no matching tag found.
+        """
+        return self._entries.get(tag_code, default)
+
 
 class _IfdParser(object):
     """
diff --git a/tests/image/test_tiff.py b/tests/image/test_tiff.py
@@ -11,6 +11,7 @@
 from mock import call
 
 from docx.compat import BytesIO
+from docx.image.constants import TIFF_TAG
 from docx.image.helpers import BIG_ENDIAN, LITTLE_ENDIAN, StreamReader
 from docx.image.tiff import (
     _IfdEntries, _IfdEntry, _IfdEntryFactory, _IfdParser, Tiff, _TiffParser
@@ -98,6 +99,17 @@ def it_makes_a_stream_reader_to_help_parse(self, mk_stream_rdr_fixture):
         StreamReader_.assert_called_once_with(stream, endian)
         assert stream_rdr is stream_rdr_
 
+    def it_knows_image_width_and_height_after_parsing(self):
+        px_width, px_height = 42, 24
+        entries = {
+            TIFF_TAG.IMAGE_WIDTH:  px_width,
+            TIFF_TAG.IMAGE_LENGTH: px_height,
+        }
+        ifd_entries = _IfdEntries(entries)
+        tiff_parser = _TiffParser(ifd_entries)
+        assert tiff_parser.px_width == px_width
+        assert tiff_parser.px_height == px_height
+
     # fixtures -------------------------------------------------------
 
     @pytest.fixture
