def text_at(self, text, position, color=(255, 255, 255),
                size=12, antialias=False, center=False):
        """Write text at x, y top left corner position.

        By default the x and y coordinates represent the top left hand corner
        of the text. The text can be centered vertically and horizontally by
        using setting the ``center`` option to ``True``.

        :param text: text to write
        :param position: (row, col) tuple
        :param color: RGB tuple
        :param size: font size
        :param antialias: whether or not the text should be antialiased
        :param center: whether or not the text should be centered on the
                       input coordinate
        """
        def antialias_value(value, normalisation):
            return int(round(value * normalisation))

        def antialias_rgb(color, normalisation):
            return tuple([antialias_value(v, normalisation) for v in color])

        def set_color(xpos, ypos, color):
            try:
                self[ypos, xpos] = color
            except IndexError:
                pass

        y, x = position
        font = PIL.ImageFont.truetype(DEFAULT_FONT_PATH, size=size)
        mask = font.getmask(text)
        width, height = mask.size
        if center:
            x = x - (width // 2)
            y = y - (height // 2)
        for ystep in range(height):
            for xstep in range(width):
                normalisation = mask[ystep * width + xstep] / 255.
                if antialias:
                    if normalisation != 0:
                        rgb_color = antialias_rgb(color, normalisation)
                        set_color(x + xstep, y+ystep, rgb_color)
                else:
                    if normalisation > .5:
                        set_color(x + xstep, y + ystep, color)
Write text at x, y top left corner position.

        By default the x and y coordinates represent the top left hand corner
        of the text. The text can be centered vertically and horizontally by
        using setting the ``center`` option to ``True``.

        :param text: text to write
        :param position: (row, col) tuple
        :param color: RGB tuple
        :param size: font size
        :param antialias: whether or not the text should be antialiased
        :param center: whether or not the text should be centered on the
                       input coordinate