Initial commit (Clean history)

path/to/venv/lib/python3.12/site-packages/docx/image/tiff.py

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+from .constants import MIME_TYPE, TIFF_FLD, TIFF_TAG
+from .helpers import BIG_ENDIAN, LITTLE_ENDIAN, StreamReader
+from .image import BaseImageHeader
+
+
+class Tiff(BaseImageHeader):
+    """Image header parser for TIFF images.
+
+    Handles both big and little endian byte ordering.
+    """
+
+    @property
+    def content_type(self):
+        """Return the MIME type of this TIFF image, unconditionally the string
+        ``image/tiff``."""
+        return MIME_TYPE.TIFF
+
+    @property
+    def default_ext(self):
+        """Default filename extension, always 'tiff' for TIFF images."""
+        return "tiff"
+
+    @classmethod
+    def from_stream(cls, stream):
+        """Return a |Tiff| instance containing the properties of the TIFF image in
+        `stream`."""
+        parser = _TiffParser.parse(stream)
+
+        px_width = parser.px_width
+        px_height = parser.px_height
+        horz_dpi = parser.horz_dpi
+        vert_dpi = parser.vert_dpi
+
+        return cls(px_width, px_height, horz_dpi, vert_dpi)
+
+
+class _TiffParser:
+    """Parses a TIFF image stream to extract the image properties found in its main
+    image file directory (IFD)"""
+
+    def __init__(self, ifd_entries):
+        super(_TiffParser, self).__init__()
+        self._ifd_entries = ifd_entries
+
+    @classmethod
+    def parse(cls, stream):
+        """Return an instance of |_TiffParser| containing the properties parsed from the
+        TIFF image in `stream`."""
+        stream_rdr = cls._make_stream_reader(stream)
+        ifd0_offset = stream_rdr.read_long(4)
+        ifd_entries = _IfdEntries.from_stream(stream_rdr, ifd0_offset)
+        return cls(ifd_entries)
+
+    @property
+    def horz_dpi(self):
+        """The horizontal dots per inch value calculated from the XResolution and
+        ResolutionUnit tags of the IFD; defaults to 72 if those tags are not present."""
+        return self._dpi(TIFF_TAG.X_RESOLUTION)
+
+    @property
+    def vert_dpi(self):
+        """The vertical dots per inch value calculated from the XResolution and
+        ResolutionUnit tags of the IFD; defaults to 72 if those tags are not present."""
+        return self._dpi(TIFF_TAG.Y_RESOLUTION)
+
+    @property
+    def px_height(self):
+        """The number of stacked rows of pixels in the image, |None| if the IFD contains
+        no ``ImageLength`` tag, the expected case when the TIFF is embeded in an Exif
+        image."""
+        return self._ifd_entries.get(TIFF_TAG.IMAGE_LENGTH)
+
+    @property
+    def px_width(self):
+        """The number of pixels in each row in the image, |None| if the IFD contains no
+        ``ImageWidth`` tag, the expected case when the TIFF is embeded in an Exif
+        image."""
+        return self._ifd_entries.get(TIFF_TAG.IMAGE_WIDTH)
+
+    @classmethod
+    def _detect_endian(cls, stream):
+        """Return either BIG_ENDIAN or LITTLE_ENDIAN depending on the endian indicator
+        found in the TIFF `stream` header, either 'MM' or 'II'."""
+        stream.seek(0)
+        endian_str = stream.read(2)
+        return BIG_ENDIAN if endian_str == b"MM" else LITTLE_ENDIAN
+
+    def _dpi(self, resolution_tag):
+        """Return the dpi value calculated for `resolution_tag`, which can be either
+        TIFF_TAG.X_RESOLUTION or TIFF_TAG.Y_RESOLUTION.
+
+        The calculation is based on the values of both that tag and the
+        TIFF_TAG.RESOLUTION_UNIT tag in this parser's |_IfdEntries| instance.
+        """
+        ifd_entries = self._ifd_entries
+
+        if resolution_tag not in ifd_entries:
+            return 72
+
+        # resolution unit defaults to inches (2)
+        resolution_unit = ifd_entries.get(TIFF_TAG.RESOLUTION_UNIT, 2)
+
+        if resolution_unit == 1:  # aspect ratio only
+            return 72
+        # resolution_unit == 2 for inches, 3 for centimeters
+        units_per_inch = 1 if resolution_unit == 2 else 2.54
+        dots_per_unit = ifd_entries[resolution_tag]
+        return int(round(dots_per_unit * units_per_inch))
+
+    @classmethod
+    def _make_stream_reader(cls, stream):
+        """Return a |StreamReader| instance with wrapping `stream` and having "endian-
+        ness" determined by the 'MM' or 'II' indicator in the TIFF stream header."""
+        endian = cls._detect_endian(stream)
+        return StreamReader(stream, endian)
+
+
+class _IfdEntries:
+    """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
+
+    def __contains__(self, key):
+        """Provides ``in`` operator, e.g. ``tag in ifd_entries``"""
+        return self._entries.__contains__(key)
+
+    def __getitem__(self, key):
+        """Provides indexed access, e.g. ``tag_value = ifd_entries[tag_code]``"""
+        return self._entries.__getitem__(key)
+
+    @classmethod
+    def from_stream(cls, stream, offset):
+        """Return a new |_IfdEntries| instance parsed from `stream` starting at
+        `offset`."""
+        ifd_parser = _IfdParser(stream, offset)
+        entries = {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:
+    """Service object that knows how to extract directory entries from an Image File
+    Directory (IFD)"""
+
+    def __init__(self, stream_rdr, offset):
+        super(_IfdParser, self).__init__()
+        self._stream_rdr = stream_rdr
+        self._offset = offset
+
+    def iter_entries(self):
+        """Generate an |_IfdEntry| instance corresponding to each entry in the
+        directory."""
+        for idx in range(self._entry_count):
+            dir_entry_offset = self._offset + 2 + (idx * 12)
+            ifd_entry = _IfdEntryFactory(self._stream_rdr, dir_entry_offset)
+            yield ifd_entry
+
+    @property
+    def _entry_count(self):
+        """The count of directory entries, read from the top of the IFD header."""
+        return self._stream_rdr.read_short(self._offset)
+
+
+def _IfdEntryFactory(stream_rdr, offset):
+    """Return an |_IfdEntry| subclass instance containing the value of the directory
+    entry at `offset` in `stream_rdr`."""
+    ifd_entry_classes = {
+        TIFF_FLD.ASCII: _AsciiIfdEntry,
+        TIFF_FLD.SHORT: _ShortIfdEntry,
+        TIFF_FLD.LONG: _LongIfdEntry,
+        TIFF_FLD.RATIONAL: _RationalIfdEntry,
+    }
+    field_type = stream_rdr.read_short(offset, 2)
+    EntryCls = ifd_entry_classes.get(field_type, _IfdEntry)
+    return EntryCls.from_stream(stream_rdr, offset)
+
+
+class _IfdEntry:
+    """Base class for IFD entry classes.
+
+    Subclasses are differentiated by value type, e.g. ASCII, long int, etc.
+    """
+
+    def __init__(self, tag_code, value):
+        super(_IfdEntry, self).__init__()
+        self._tag_code = tag_code
+        self._value = value
+
+    @classmethod
+    def from_stream(cls, stream_rdr, offset):
+        """Return an |_IfdEntry| subclass instance containing the tag and value of the
+        tag parsed from `stream_rdr` at `offset`.
+
+        Note this method is common to all subclasses. Override the ``_parse_value()``
+        method to provide distinctive behavior based on field type.
+        """
+        tag_code = stream_rdr.read_short(offset, 0)
+        value_count = stream_rdr.read_long(offset, 4)
+        value_offset = stream_rdr.read_long(offset, 8)
+        value = cls._parse_value(stream_rdr, offset, value_count, value_offset)
+        return cls(tag_code, value)
+
+    @classmethod
+    def _parse_value(cls, stream_rdr, offset, value_count, value_offset):
+        """Return the value of this field parsed from `stream_rdr` at `offset`.
+
+        Intended to be overridden by subclasses.
+        """
+        return "UNIMPLEMENTED FIELD TYPE"  # pragma: no cover
+
+    @property
+    def tag(self):
+        """Short int code that identifies this IFD entry."""
+        return self._tag_code
+
+    @property
+    def value(self):
+        """Value of this tag, its type being dependent on the tag."""
+        return self._value
+
+
+class _AsciiIfdEntry(_IfdEntry):
+    """IFD entry having the form of a NULL-terminated ASCII string."""
+
+    @classmethod
+    def _parse_value(cls, stream_rdr, offset, value_count, value_offset):
+        """Return the ASCII string parsed from `stream_rdr` at `value_offset`.
+
+        The length of the string, including a terminating '\x00' (NUL) character, is in
+        `value_count`.
+        """
+        return stream_rdr.read_str(value_count - 1, value_offset)
+
+
+class _ShortIfdEntry(_IfdEntry):
+    """IFD entry expressed as a short (2-byte) integer."""
+
+    @classmethod
+    def _parse_value(cls, stream_rdr, offset, value_count, value_offset):
+        """Return the short int value contained in the `value_offset` field of this
+        entry.
+
+        Only supports single values at present.
+        """
+        if value_count == 1:
+            return stream_rdr.read_short(offset, 8)
+        else:  # pragma: no cover
+            return "Multi-value short integer NOT IMPLEMENTED"
+
+
+class _LongIfdEntry(_IfdEntry):
+    """IFD entry expressed as a long (4-byte) integer."""
+
+    @classmethod
+    def _parse_value(cls, stream_rdr, offset, value_count, value_offset):
+        """Return the long int value contained in the `value_offset` field of this
+        entry.
+
+        Only supports single values at present.
+        """
+        if value_count == 1:
+            return stream_rdr.read_long(offset, 8)
+        else:  # pragma: no cover
+            return "Multi-value long integer NOT IMPLEMENTED"
+
+
+class _RationalIfdEntry(_IfdEntry):
+    """IFD entry expressed as a numerator, denominator pair."""
+
+    @classmethod
+    def _parse_value(cls, stream_rdr, offset, value_count, value_offset):
+        """Return the rational (numerator / denominator) value at `value_offset` in
+        `stream_rdr` as a floating-point number.
+
+        Only supports single values at present.
+        """
+        if value_count == 1:
+            numerator = stream_rdr.read_long(value_offset)
+            denominator = stream_rdr.read_long(value_offset, 4)
+            return numerator / denominator
+        else:  # pragma: no cover
+            return "Multi-value Rational NOT IMPLEMENTED"