Class _Chunks

src/docx/image/png.py:92–126

Collection of the chunks parsed from a PNG image stream.

class _Chunks:
    """Collection of the chunks parsed from a PNG image stream."""

    def __init__(self, chunk_iterable):
        super(_Chunks, self).__init__()
        self._chunks = list(chunk_iterable)

    @classmethod
    def from_stream(cls, stream):
        """Return a |_Chunks| instance containing the PNG chunks in `stream`."""
        chunk_parser = _ChunkParser.from_stream(stream)
        chunks = list(chunk_parser.iter_chunks())
        return cls(chunks)

    @property
    def IHDR(self):
        """IHDR chunk in PNG image."""
        match = lambda chunk: chunk.type_name == PNG_CHUNK_TYPE.IHDR  # noqa
        IHDR = self._find_first(match)
        if IHDR is None:
            raise InvalidImageStreamError("no IHDR chunk in PNG image")
        return IHDR

    @property
    def pHYs(self):
        """PHYs chunk in PNG image, or |None| if not present."""
        match = lambda chunk: chunk.type_name == PNG_CHUNK_TYPE.pHYs  # noqa
        return self._find_first(match)

    def _find_first(self, match):
        """Return first chunk in stream order returning True for function `match`."""
        for chunk in self._chunks:
            if match(chunk):
                return chunk
        return None


class _ChunkParser: