Method write

_plotly_utils/png.py:626–677

Write a PNG image to the output file. `rows` should be an iterable that yields each row (each row is a sequence of values). The rows should be the rows of the original image, so there should be ``self.height`` rows of ``self.width * self.planes`` valu

(self, outfile, rows)

        self.psize = (self.bitdepth / 8) * self.planes

    def write(self, outfile, rows):
        """
        Write a PNG image to the output file.
        `rows` should be an iterable that yields each row
        (each row is a sequence of values).
        The rows should be the rows of the original image,
        so there should be ``self.height`` rows of
        ``self.width * self.planes`` values.
        If `interlace` is specified (when creating the instance),
        then an interlaced PNG file will be written.
        Supply the rows in the normal image order;
        the interlacing is carried out internally.

        .. note ::

          Interlacing requires the entire image to be in working memory.
        """

        # Values per row
        vpr = self.width * self.planes

        def check_rows(rows):
            """
            Yield each row in rows,
            but check each row first (for correct width).
            """
            for i, row in enumerate(rows):
                try:
                    wrong_length = len(row) != vpr
                except TypeError:
                    # When using an itertools.ichain object or
                    # other generator not supporting __len__,
                    # we set this to False to skip the check.
                    wrong_length = False
                if wrong_length:
                    # Note: row numbers start at 0.
                    raise ProtocolError(
                        "Expected %d values but got %d values, in row %d"
                        % (vpr, len(row), i)
                    )
                yield row

        if self.interlace:
            fmt = "BH"[self.bitdepth > 8]
            a = array(fmt, itertools.chain(*check_rows(rows)))
            return self.write_array(outfile, a)

        nrows = self.write_passes(outfile, check_rows(rows))
        if nrows != self.height:
            raise ProtocolError(
                "rows supplied (%d) does not match height (%d)" % (nrows, self.height)
            )

    def write_passes(self, outfile, rows):
        """