writers.py

# -*- coding: utf-8 -*-
#
# Copyright (c) 2016 - 2020 -- Lars Heuer
# All rights reserved.
#
# License: BSD License
#
"""\
Standard serializers and utility functions for serializers.

DOES NOT belong to the public API.

The serializers are independent of the :py:class:`segno.QRCode` (and the
:py:class:`segno.encoder.Code`) class; they just need a matrix (tuple of
bytearrays) and the version constant.
"""
from __future__ import absolute_import, unicode_literals, division
import io
import re
import zlib
import codecs
import base64
import gzip
from xml.sax.saxutils import quoteattr, escape
from struct import pack
from itertools import chain, repeat
import functools
from functools import partial
from functools import reduce
from operator import itemgetter
from contextlib import contextmanager
from collections import defaultdict
import time
_PY2 = False
try:  # pragma: no cover
    from itertools import zip_longest
    from urllib.parse import quote
except ImportError:  # pragma: no cover
    _PY2 = True
    from itertools import izip_longest as zip_longest
    from urllib import quote
    range = xrange
    str = unicode
    from io import open
from . import consts
from .utils import matrix_to_lines, get_symbol_size, get_border, \
        check_valid_scale, check_valid_border, matrix_iter, matrix_iter_verbose

__all__ = ('writable', 'write_svg', 'write_png', 'write_eps', 'write_pdf',
           'write_txt', 'write_pbm', 'write_pam', 'write_ppm', 'write_xpm',
           'write_xbm', 'write_tex', 'write_terminal')

# Standard creator name
CREATOR = 'Segno <https://pypi.org/project/segno/>'


@contextmanager
def writable(file_or_path, mode, encoding=None):
    """\
    Returns a writable file-like object.

    Usage::

        with writable(file_name_or_path, 'wb') as f:
            ...


    :param file_or_path: Either a file-like object or a filename.
    :param str mode: String indicating the writing mode (i.e. ``'wb'``)
    """
    f = file_or_path
    must_close = False
    try:
        file_or_path.write
        if encoding is not None:
            f = codecs.getwriter(encoding)(file_or_path)
    except AttributeError:
        f = open(file_or_path, mode, encoding=encoding)
        must_close = True
    try:
        yield f
    finally:
        if must_close:
            f.close()


def colorful(dark, light):
    """\
    Decorator to inject a module type -> color mapping into the decorated function.
    """
    def decorate(f):
        @functools.wraps(f)
        def wrapper(matrix, version, out, dark=dark, light=light, finder_dark=False, finder_light=False,
                    data_dark=False, data_light=False, version_dark=False, version_light=False,
                    format_dark=False, format_light=False, alignment_dark=False, alignment_light=False,
                    timing_dark=False, timing_light=False, separator=False, dark_module=False,
                    quiet_zone=False, **kw):
            cm = _make_colormap(version, dark=dark, light=light, finder_dark=finder_dark,
                                finder_light=finder_light, data_dark=data_dark,
                                data_light=data_light, version_dark=version_dark,
                                version_light=version_light, format_dark=format_dark,
                                format_light=format_light, alignment_dark=alignment_dark,
                                alignment_light=alignment_light, timing_dark=timing_dark,
                                timing_light=timing_light, separator=separator,
                                dark_module=dark_module, quiet_zone=quiet_zone)
            return f(matrix, version, out, cm, **kw)
        if _PY2:  # pragma: no cover
            wrapper.__wrapped__ = f  # Needed by CLI to inspect the arguments
        return wrapper
    return decorate


def _valid_width_height_and_border(version, scale, border):
    """"\
    Validates the scale and border and returns the width, height and the border.
    If the border is ``None´` the default border is returned.
    """
    check_valid_scale(scale)
    check_valid_border(border)
    border = get_border(version, border)
    width, height = get_symbol_size(version, scale, border)
    return width, height, border


@colorful(dark='#000', light=None)
def write_svg(matrix, version, out, colormap, scale=1, border=None, xmldecl=True,
              svgns=True, title=None, desc=None, svgid=None, svgclass='segno',
              lineclass='qrline', omitsize=False, unit=None, encoding='utf-8',
              svgversion=None, nl=True, draw_transparent=False):
    """\
    Serializes the QR Code as SVG document.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write bytes.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 pixel per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param bool xmldecl: Inidcates if the XML declaration header should be
            written (default: ``True``)
    :param bool svgns: Indicates if the SVG namespace should be written
            (default: ``True``).
    :param str title: Optional title of the generated SVG document.
    :param str desc: Optional description of the generated SVG document.
    :param svgid: The ID of the SVG document (if set to ``None`` (default),
            the SVG element won't have an ID).
    :param svgclass: The CSS class of the SVG document
            (if set to ``None``, the SVG element won't have a class).
    :param lineclass: The CSS class of the path element (which draws the
            "black" modules (if set to ``None``, the path won't have a class).
    :param bool omitsize: Indicates if width and height attributes should be
            omitted (default: ``False``). If these attributes are omitted,
            a ``viewBox`` attribute will be added to the document.
    :param str unit: Unit for width / height and other coordinates.
            By default, the unit is unspecified and all values are
            in the user space.
            Valid values: em, ex, px, pt, pc, cm, mm, in, and percentages
    :param str encoding: Encoding of the XML document. "utf-8" by default.
    :param float svgversion: SVG version (default: None)
    :param bool nl: Indicates if the document should have a trailing newline
            (default: ``True``)
    :param bool draw_transparent: Indicates if transparent SVG paths should be
            added to the graphic (default: ``False``)
    """
    def svg_color(clr):
        return _color_to_webcolor(clr, allow_css3_colors=allow_css3_colors) if clr is not None else None

    def matrix_to_lines_verbose():
        j = -.5  # stroke width / 2
        invalid_color = -1
        for row in matrix_iter_verbose(matrix, version, scale=1, border=border):
            last_color = invalid_color
            x1, x2 = 0, 0
            j += 1
            for c in (colormap[mt] for mt in row):
                if last_color != invalid_color and last_color != c:
                    yield last_color, (x1, x2, j)
                    x1 = x2
                x2 += 1
                last_color = c
            yield last_color, (x1, x2, j)

    width, height, border = _valid_width_height_and_border(version, scale, border)
    unit = unit or ''
    if unit and omitsize:
        raise ValueError('The unit "{}" has no effect if the size '
                         '(width and height) is omitted.'.format(unit))
    omit_encoding = encoding is None
    if omit_encoding:
        encoding = 'utf-8'
    allow_css3_colors = svgversion is not None and svgversion >= 2.0
    is_multicolor = len(set(colormap.values())) > 2
    need_background = not is_multicolor and colormap[consts.TYPE_QUIET_ZONE] is not None and not draw_transparent
    need_svg_group = scale != 1 and (need_background or is_multicolor)
    if is_multicolor:
        miter = matrix_to_lines_verbose()
    else:
        x, y = border, border + .5
        dark = colormap[consts.TYPE_DATA_DARK]
        miter = ((dark, (x1, x2, y1)) for (x1, y1), (x2, y2) in matrix_to_lines(matrix, x, y))
    xy = defaultdict(lambda: (0, 0))
    coordinates = defaultdict(list)
    for clr, (x1, x2, y1) in miter:
        x, y = xy[clr]
        coordinates[clr].append((x1 - x, y1 - y, x2 - x1))
        xy[clr] = x2, y1
    if need_background:
        # Add an additional path for the background, will be modified after
        # the SVG paths have been generated
        coordinates[colormap[consts.TYPE_QUIET_ZONE]] = [(0, 0, width // scale)]
    if not draw_transparent:
        try:
            del coordinates[None]
        except KeyError:
            pass
    paths = {}
    scale_info = ' transform="scale({})"'.format(scale) if scale != 1 else ''
    p = '<path{}{}'.format(scale_info if not need_svg_group else '',
                           '' if not lineclass else ' class={}'.format(quoteattr(lineclass)))
    for color, coord in coordinates.items():
        path = p
        clr = svg_color(color)
        if clr is not None:
            opacity = None
            if isinstance(clr, tuple):
                clr, opacity = clr
            path += ' stroke={}'.format(quoteattr(clr))
            if opacity is not None:
                path += ' stroke-opacity={}'.format(quoteattr(str(opacity)))
        path += ' d="'
        path += ''.join('{moveto}{x} {y}h{l}'.format(moveto=('m' if i > 0 else 'M'),
                                                     x=x, l=length,
                                                     y=(int(y) if int(y) == y else y))
                        for i, (x, y, length) in enumerate(coord))
        path += '"/>'
        paths[color] = path
    if need_background:
        # This code is necessary since the path was generated by the loop above
        # but the background path is special: It has no stroke- but a fill-color
        # and it needs to be closed. Further, it has no class attribute.
        k = colormap[consts.TYPE_QUIET_ZONE]
        paths[k] = re.sub(r'\sclass="[^"]+"', '',
                          paths[k].replace('stroke', 'fill')
                                  .replace('"/>', 'v{0}h-{1}z"/>'.format(height // scale, width // scale)))
    svg = ''
    if xmldecl:
        svg += '<?xml version="1.0"'
        if not omit_encoding:
            svg += ' encoding={}'.format(quoteattr(encoding))
        svg += '?>\n'
    svg += '<svg'
    if svgns:
        svg += ' xmlns="http://www.w3.org/2000/svg"'
    if svgversion is not None and svgversion < 2.0:
        svg += ' version={}'.format(quoteattr(str(svgversion)))
    if not omitsize:
        svg += ' width="{0}{2}" height="{1}{2}"'.format(width, height, unit)
    if omitsize or unit:
        svg += ' viewBox="0 0 {} {}"'.format(width, height)
    if svgid:
        svg += ' id={}'.format(quoteattr(svgid))
    if svgclass:
        svg += ' class={}'.format(quoteattr(svgclass))
    svg += '>'
    if title is not None:
        svg += '<title>{}</title>'.format(escape(title))
    if desc is not None:
        svg += '<desc>{}</desc>'.format(escape(desc))
    if need_svg_group:
        svg += '<g{}>'.format(scale_info)
    svg += ''.join(sorted(paths.values(), key=len))
    if need_svg_group:
        svg += '</g>'
    svg += '</svg>'
    if nl:
        svg += '\n'
    with writable(out, 'wt', encoding=encoding) as f:
        f.write(svg)


_replace_quotes = partial(re.compile(br'(=)"([^"]+)"').sub, br"\1'\2'")

def as_svg_data_uri(matrix, version, scale=1, border=None,
                    xmldecl=False, svgns=True, title=None,
                    desc=None, svgid=None, svgclass='segno',
                    lineclass='qrline', omitsize=False, unit='',
                    encoding='utf-8', svgversion=None, nl=False,
                    encode_minimal=False, omit_charset=False, **kw):
    """\
    Converts the matrix to a SVG data URI.

    The XML declaration is omitted by default (set ``xmldecl`` to ``True``
    to enable it), further the newline is omitted by default (set ``nl`` to
    ``True`` to enable it).

    Aside from the missing ``out`` parameter and the different ``xmldecl``
    and ``nl`` default values and the additional parameter ``encode_minimal``
    and ``omit_charset`` this function uses the same parameters as the
    usual SVG serializer.

    :param bool encode_minimal: Indicates if the resulting data URI should
                    use minimal percent encoding (disabled by default).
    :param bool omit_charset: Indicates if the ``;charset=...`` should be omitted
                    (disabled by default)
    :rtype: str
    """
    encode = partial(quote, safe=b"") if not encode_minimal else partial(quote, safe=b" :/='")
    buff = io.BytesIO()
    write_svg(matrix, version, buff, scale=scale, border=border, xmldecl=xmldecl,
              svgns=svgns, title=title, desc=desc, svgclass=svgclass,
              lineclass=lineclass, omitsize=omitsize, encoding=encoding,
              svgid=svgid, unit=unit, svgversion=svgversion, nl=nl, **kw)
    return 'data:image/svg+xml{0},{1}' \
                .format(';charset=' + encoding if not omit_charset else '',
                        # Replace " quotes with ' and URL encode the result
                        # See also https://codepen.io/tigt/post/optimizing-svgs-in-data-uris
                        encode(_replace_quotes(buff.getvalue())))


def write_svg_debug(matrix, version, out, scale=15, border=None,
                    fallback_color='fuchsia', colormap=None,
                    add_legend=True):  # pragma: no cover
    """\
    Internal SVG serializer which is useful for debugging purposes.

    This function is not exposed to the QRCode class by intention and the
    resulting SVG document is very inefficient (a lot of ``<rect/>`` elements).
    Dark modules are black and light modules are white by default. Provide
    a custom `colormap` to override these defaults.
    Unknown modules are red by default.

    :param matrix: The matrix
    :param version: Version constant
    :param out: binary file-like object or file name
    :param scale: Scaling factor
    :param border: Quiet zone
    :param fallback_color: Color which is used for modules which are not 0x0 or 0x1
                and for which no entry in `color_mapping` is defined.
    :param colormap: dict of module values to color mapping (optional)
    :param bool add_legend: Indicates if the bit values should be added to the
                matrix (default: True)
    """
    clr_mapping = {
        0x0: '#fff',
        0x1: '#000',
        0x2: 'red',
        0x3: 'orange',
        0x4: 'gold',
        0x5: 'green',
    }
    if colormap is not None:
        clr_mapping.update(colormap)
    width, height, border = _valid_width_height_and_border(version, scale, border)
    matrix_size = get_symbol_size(version, scale=1, border=0)[0]
    with writable(out, 'wt', encoding='utf-8') as f:
        legend = []
        write = f.write
        write('<?xml version="1.0" encoding="utf-8"?>\n')
        write('<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 {0} {1}">'.format(width, height))
        write('<style type="text/css"><![CDATA[ text { font-size: 1px; font-family: Helvetica, Arial, sans; } ]]></style>')
        write('<g transform="scale({0})">'.format(scale))
        for i in range(matrix_size):
            y = i + border
            for j in range(matrix_size):
                x = j + border
                bit = matrix[i][j]
                if add_legend and bit not in (0x0, 0x1):
                    legend.append((x, y, bit))
                fill = clr_mapping.get(bit, fallback_color)
                write('<rect x="{0}" y="{1}" width="1" height="1" fill="{2}"/>'.format(x, y, fill))
        # legend may be empty if add_legend == False
        for x, y, val in legend:
            write('<text x="{0}" y="{1}">{2}</text>'.format(x+.2, y+.9, val))
        write('</g></svg>\n')


def write_eps(matrix, version, out, scale=1, border=None, dark='#000', light=None):
    """\
    Serializes the QR Code as EPS document.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write strings.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 point (1/72 inch) per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param dark: Color of the modules (default: black). The
            color can be provided as ``(R, G, B)`` tuple (this method
            acceppts floats as R, G, B values), as web color name (like
            "red") or in hexadecimal format (``#RGB`` or ``#RRGGBB``).
    :param light: Optional background color (default: ``None`` = no
            background color). See `color` for valid values.
    """
    import textwrap

    def write_line(writemeth, content):
        """\
        Writes `content` and ``LF``.
        """
        # Postscript: Max. 255 characters per line
        for line in textwrap.wrap(content, 254):
            writemeth(line)
            writemeth('\n')

    def rgb_to_floats(clr):
        """\
        Converts the provided color into an acceptable format for Postscript's
         ``setrgbcolor``
        """
        def to_float(c):
            if isinstance(c, float):
                if not 0.0 <= c <= 1.0:
                    raise ValueError('Invalid color "{0}". Not in range 0 .. 1'
                                     .format(c))
                return c
            return 1 / 255.0 * c if c != 1 else c

        return tuple([to_float(i) for i in _color_to_rgb(clr)])

    width, height, border = _valid_width_height_and_border(version, scale, border)
    stroke_color_is_black = _color_is_black(dark)
    stroke_color = dark if stroke_color_is_black else rgb_to_floats(dark)
    with writable(out, 'wt') as f:
        writeline = partial(write_line, f.write)
        writeline('%!PS-Adobe-3.0 EPSF-3.0')
        writeline('%%Creator: {0}'.format(CREATOR))
        writeline('%%CreationDate: {0}'.format(time.strftime("%Y-%m-%d %H:%M:%S")))
        writeline('%%DocumentData: Clean7Bit')
        writeline('%%BoundingBox: 0 0 {0} {1}'.format(width, height))
        # Write the shortcuts
        writeline('/m { rmoveto } bind def')
        writeline('/l { rlineto } bind def')
        if light is not None:
            writeline('{0:f} {1:f} {2:f} setrgbcolor clippath fill'
                      .format(*rgb_to_floats(light)))
            if stroke_color_is_black:
                # Reset RGB color back to black iff stroke color is black
                # In case stroke color != black set the RGB color later
                writeline('0 0 0 setrgbcolor')
        if not stroke_color_is_black:
            writeline('{0:f} {1:f} {2:f} setrgbcolor'.format(*stroke_color))
        if scale != 1:
            writeline('{0} {0} scale'.format(scale))
        writeline('newpath')
        # Current pen position y-axis
        # Note: 0, 0 = lower left corner in PS coordinate system
        y = get_symbol_size(version, scale=1, border=0)[1] + border - .5  # .5 = linewidth / 2
        line_iter = matrix_to_lines(matrix, border, y, incby=-1)
        # EPS supports absolute coordinates as well, but relative coordinates
        # are more compact and IMO nicer; so the 1st coordinate is absolute, all
        # other coordinates are relative
        (x1, y1), (x2, y2) = next(line_iter)
        coord = ['{0} {1} moveto {2} 0 l'.format(x1, y1, x2 - x1)]
        append_coord = coord.append
        x = x2
        for (x1, y1), (x2, y2) in line_iter:
            append_coord(' {0} {1} m {2} 0 l'.format(x1 - x, int(y1 - y), x2 - x1))
            x, y = x2, y2
        writeline(''.join(coord))
        writeline('stroke')
        writeline('%%EOF')


def as_png_data_uri(matrix, version, scale=1, border=None,
                    compresslevel=9, **kw):
    """\
    Converts the provided matrix into a PNG data URI.

    See :func:`write_png` for a description of supported parameters.

    :rtype: str
    """
    buff = io.BytesIO()
    write_png(matrix, version, buff, scale=scale, border=border,
              compresslevel=compresslevel, **kw)
    return 'data:image/png;base64,{0}' \
                .format(base64.b64encode(buff.getvalue()).decode('ascii'))


@colorful(dark='#000', light='#fff')
def write_png(matrix, version, out, colormap, scale=1, border=None,
              compresslevel=9, dpi=None):
    """\
    Serializes the QR Code as PNG image.

    By default, the generated PNG will be a greyscale image (black / white)
    with a bit depth of 1. If different colors are provided, an indexed-color
    image with the same bit depth is generated unless more than two colors
    are provided. This may require a bit depth of of 2 or 4.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write bytes.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 pixel per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param int dpi: Optional DPI setting. By default (``None``), the PNG won't
            have any DPI information. Note that the DPI value is converted into
            meters since PNG does not support any DPI information.
    :param int compresslevel: Integer indicating the compression level
            (default: 9). 1 is fastest and produces the least
            compression, 9 is slowest and produces the most.
            0 is no compression.
    :param dict colormap: Optional module type -> color mapping. If provided, the
            `color` and `background` arguments are ignored. All undefined module
            types will have the default colors (light: white, dark: black).
            See `color` for valid color values. ``None`` is accepted as valid
            color value as well (becomes transparent).
    """

    def png_color(clr):
        return _color_to_rgb_or_rgba(clr, alpha_float=False) if clr is not None else transparent

    def chunk(name, data):
        """\
        Returns a PNG chunk with checksum.
        """
        chunk_head = name + data
        # See <https://docs.python.org/2/library/zlib.html#zlib.crc32>
        # why crc32() & 0xFFFFFFFF is necessary
        return pack(b'>I', len(data)) + chunk_head \
               + pack(b'>I', zlib.crc32(chunk_head) & 0xFFFFFFFF)

    def scale_row_x_axis(row):
        """\
        Returns each pixel `scale` times.
        """
        return chain(*(repeat(b, scale) for b in row))

    def scanline(row, filter_type=b'\0'):
        """\
        Returns a single scanline.
        """
        return bytearray(chain(filter_type,
                               # See _pack_bits_into_byte, same code, but the bit depth is taken
                               # into account
                               (reduce(lambda x, y: (x << png_bit_depth) + y, e)
                                for e in zip_longest(*[iter(row)] * (8 // png_bit_depth), fillvalue=0x0))))

    scale = int(scale)
    width, height, border = _valid_width_height_and_border(version, scale, border)
    if dpi:
        dpi = int(dpi)
        if dpi < 0:
            raise ValueError('DPI value must not be negative')
        dpi = int(dpi // 0.0254)

    black = (0, 0, 0)
    white = (255, 255, 255)
    transparent = (-1, -1, -1, -1)  # Invalid placeholder for transparent color
    dark_idx = consts.TYPE_FINDER_PATTERN_DARK
    qz_idx = consts.TYPE_QUIET_ZONE
    for mt, clr in colormap.items():
        colormap[mt] = png_color(clr)
    # Creating a palette here regardless of the image type (greyscale vs. index-colors)
    palette = sorted(set(colormap.values()), key=itemgetter(0, 1, 2))
    is_transparent = transparent in palette
    number_of_colors = len(palette)
    # Check if greyscale mode is applicable
    is_greyscale = number_of_colors == 2 and all(clr in (transparent, black, white) for clr in palette)
    png_color_type = 0 if is_greyscale else 3
    png_bit_depth = 1  # Assume a bit depth of 1 (may change if PLTE is used)
    png_trans_idx = None
    if not is_greyscale:  # PLTE
        if number_of_colors > 2:
            # Max. 15 different colors are supported, no need to support
            # bit depth 8 (more than 16 colors)
            png_bit_depth = 2 if number_of_colors < 5 else 4
        palette.sort(key=len, reverse=True)  # RGBA colors first
        if is_transparent:
            png_trans_idx = 0
            need_rgba = len(palette[1]) == 4
            transparent_color = None
            # Choose a random color which becomes transparent. TODO: Better alternatives? More elegant code?
            for clr_val in _NAME2RGB.values():
                if need_rgba:
                    clr_val += (0,)
                if clr_val not in palette:
                    transparent_color = clr_val
                    break
            palette[0] = transparent_color
            for module_type, clr in colormap.items():
                if clr == transparent:
                    colormap[module_type] = transparent_color
    elif is_transparent:  # Greyscale and transparent
        if black in palette:
            # Since black is zero, it should be the first entry
            palette = [black, transparent]
        png_trans_idx = palette.index(transparent)
    # Keeps a mapping of iterator output -> color number
    color_index = {}
    if number_of_colors > 2:
        # Need the more expensive matrix iterator
        miter = matrix_iter_verbose(matrix, version, scale=1, border=0)
        for module_type, clr in colormap.items():
            color_index[module_type] = palette.index(clr)
    else:
        # Just two colors, use the cheap iterator which returns 0x0 or 0x1
        miter = iter(matrix)
        # The code to create the image requires that TYPE_QUIET_ZONE is available
        color_index[qz_idx] = palette.index(colormap[qz_idx])
        color_index[0] = color_index[qz_idx]
        color_index[1] = palette.index(colormap[dark_idx])
    miter = ((color_index[b] for b in r) for r in miter)
    horizontal_border = b''
    vertical_border = b''
    if border > 0:
        # Calculate horizontal and vertical border
        qz_value = color_index[qz_idx]
        horizontal_border = scanline(repeat(qz_value, width)) * border * scale
        vertical_border = [qz_value] * border * scale
    # <https://www.w3.org/TR/PNG/#9Filters>
    # This variable holds the "Up" filter which indicates that this scanline
    # is equal to the above scanline (since it is filled with null bytes)
    same_as_above = b''
    if scale > 1:
        # 2 == PNG Filter "Up"  <https://www.w3.org/TR/PNG/#9-table91>
        same_as_above = scanline(repeat(0x0, width), filter_type=b'\2') * (scale - 1)
        miter = map(scale_row_x_axis, miter)
    idat = bytearray(horizontal_border)
    for row in miter:
        # Chain precalculated left border with row and right border
        idat += scanline(chain(vertical_border, row, vertical_border))
        idat += same_as_above  # This is b'' if no scaling factor was provided
    idat += horizontal_border
    if _PY2:  # pragma: no cover
        idat = bytes(idat)
    with writable(out, 'wb') as f:
        write = f.write
        write(b'\211PNG\r\n\032\n')  # Magic number
        # Header:
        # width, height, bitdepth, colortype, compression meth., filter, interlance
        write(chunk(b'IHDR', pack(b'>2I5B', width, height, png_bit_depth, png_color_type, 0, 0, 0)))
        if dpi:
            write(chunk(b'pHYs', pack(b'>LLB', dpi, dpi, 1)))
        if not is_greyscale:
            write(chunk(b'PLTE', b''.join(pack(b'>3B', *clr[:3]) for clr in palette)))
            # <https://www.w3.org/TR/PNG/#11tRNS>
            if len(palette[0]) > 3:  # Color with alpha channel is the first entry in the palette
                write(chunk(b'tRNS', b''.join(pack(b'>B', clr[3]) for clr in palette if len(clr) > 3)))
            elif is_transparent:
                write(chunk(b'tRNS', pack(b'>B', png_trans_idx)))
        elif is_transparent:
            # Grayscale with Transparency
            # <https://www.w3.org/TR/PNG/#11tRNS>
            # 2 bytes for color type == 0 (greyscale)
            write(chunk(b'tRNS', pack(b'>1H', png_trans_idx)))
        write(chunk(b'IDAT', zlib.compress(idat, compresslevel)))
        write(chunk(b'IEND', b''))


def write_pdf(matrix, version, out, scale=1, border=None, dark='#000',
              light=None, compresslevel=9):
    """\
    Serializes the QR Code as PDF document.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write bytes.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 pixel per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param dark: Color of the modules (default: black). The
            color can be provided as ``(R, G, B)`` tuple, as web color name
            (like "red") or in hexadecimal format (``#RGB`` or ``#RRGGBB``).
    :param light: Optional background color (default: ``None`` = no
            background color). See `color` for valid values.
    :param int compresslevel: Integer indicating the compression level
            (default: 9). 1 is fastest and produces the least
            compression, 9 is slowest and produces the most.
            0 is no compression.
    """

    def write_string(writemeth, s):
        writemeth(s.encode('ascii'))

    def to_pdf_color(clr):
        """\
        Converts the provided color into an acceptable format for PDF's
        "DeviceRGB" color space.
        """
        def to_float(c):
            if isinstance(c, float):
                if not 0.0 <= c <= 1.0:
                    raise ValueError('Invalid color "{0}". Not in range 0 .. 1'
                                     .format(c))
                return c
            return 1 / 255.0 * c if c != 1 else c
        return tuple([to_float(i) for i in _color_to_rgb(clr)])

    width, height, border = _valid_width_height_and_border(version, scale, border)
    creation_date = "{0}{1:+03d}'{2:02d}'".format(time.strftime('%Y%m%d%H%M%S'),
                                                  time.timezone // 3600,
                                                  abs(time.timezone) % 60)
    cmds = []
    append_cmd = cmds.append
    if scale > 1:
        append_cmd('{0} 0 0 {0} 0 0 cm'.format(scale))
    if light is not None:
        # If the background color is defined, a rect is drawn in the background
        append_cmd('{} {} {} rg'.format(*to_pdf_color(light)))
        append_cmd('0 0 {} {} re'.format(width, height))
        append_cmd('f q')
    # Set the stroke color only iff it is not black (default)
    if not _color_is_black(dark):
        append_cmd('{} {} {} RG'.format(*to_pdf_color(dark)))
    # Current pen position y-axis
    # Note: 0, 0 = lower left corner in PDF coordinate system
    y = get_symbol_size(version, scale=1, border=0)[1] + border - .5
    # Set the origin in the upper left corner
    append_cmd('1 0 0 1 {0} {1} cm'.format(border, y))
    miter = matrix_to_lines(matrix, 0, 0, incby=-1)
    # PDF supports absolute coordinates, only
    cmds.extend('{0} {1} m {2} {1} l'.format(x1, y1, x2, y2) for (x1, y1), (x2, y2) in miter)
    append_cmd('S')
    graphic = zlib.compress((' '.join(cmds)).encode('ascii'), compresslevel)
    with writable(out, 'wb') as f:
        write = f.write
        writestr = partial(write_string, write)
        object_pos = []
        write(b'%PDF-1.4\r%\xE2\xE3\xCF\xD3\r\n')
        for obj in ('obj <</Type /Catalog /Pages 2 0 R>>\r\nendobj\r\n',
                    'obj <</Type /Pages /Kids [3 0 R] /Count 1>>\r\nendobj\r\n',
                    'obj <</Type /Page /Parent 2 0 R /MediaBox [0 0 {0} {1}] /Contents 4 0 R>>\r\nendobj\r\n'.format(width, height),
                    'obj <</Length {0} /Filter /FlateDecode>>\r\nstream\r\n'.format(len(graphic))):
            object_pos.append(f.tell())
            writestr('{0} 0 {1}'.format(len(object_pos), obj))
        write(graphic)
        write(b'\r\nendstream\r\nendobj\r\n')
        object_pos.append(f.tell())
        writestr('{0} 0 obj <</CreationDate(D:{1})/Producer({2})/Creator({2})\r\n>>\r\nendofbj\r\n' \
                 .format(len(object_pos), creation_date, CREATOR))
        object_pos.append(f.tell())
        xref_location = f.tell()
        writestr('xref\r\n0 {0}\r\n0000000000 65535 f\r\n'.format(len(object_pos) + 1))
        for pos in object_pos:
            writestr('{0:010d} {1:05d} n\r\n'.format(pos, 0))
        writestr('trailer <</Size {0}/Root 1 0 R/Info 5 0 R>>\r\n'.format(len(object_pos) + 1))
        writestr('startxref\r\n{0}\r\n%%EOF\r\n'.format(xref_location))


def write_txt(matrix, version, out, border=None, dark='1', light='0'):
    """\
    Serializes QR code in a text format.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write text.
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param dark: Character to use for the black modules (default: '1')
    :param light: Character to use for the white modules (default: '0')
    """
    row_iter = matrix_iter(matrix, version, scale=1, border=border)
    colours = (str(light), str(dark))
    with writable(out, 'wt') as f:
        write = f.write
        for row in row_iter:
            write(''.join(colours[i] for i in row))
            write('\n')


def write_pbm(matrix, version, out, scale=1, border=None, plain=False):
    """\
    Serializes the matrix as `PBM <http://netpbm.sourceforge.net/doc/pbm.html>`_
    image.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write binary data.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 pixel per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param bool plain: Indicates if a P1 (ASCII encoding) image should be
            created (default: False). By default a (binary) P4 image is created.
    """
    def pack_row(iterable):
        """\
        Packs eight bits into one byte.
        """
        return (reduce(lambda x, y: (x << 1) + y, e)
                for e in zip_longest(*[iter(iterable)] * 8, fillvalue=0x0))

    width, height, border = _valid_width_height_and_border(version, scale, border)
    row_iter = matrix_iter(matrix, version, scale, border)
    with writable(out, 'wb') as f:
        write = f.write
        write('{0}\n'
              '# Created by {1}\n'
              '{2} {3}\n'\
              .format(('P4' if not plain else 'P1'), CREATOR, width, height).encode('ascii'))
        if not plain:
            for row in row_iter:
                write(bytearray(pack_row(row)))
        else:
            for row in row_iter:
                write(b''.join(str(i).encode('ascii') for i in row))
                write(b'\n')


def write_pam(matrix, version, out, scale=1, border=None, dark='#000', light='#fff'):
    """\
    Serializes the matrix as `PAM <http://netpbm.sourceforge.net/doc/pam.html>`_
    image.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write binary data.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 pixel per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param dark: Color of the modules (default: black). The
            color can be provided as ``(R, G, B)`` tuple, as web color name
            (like "red") or in hexadecimal format (``#RGB`` or ``#RRGGBB``).
    :param light: Optional background color (default: white).
            See `color` for valid values. In addition, ``None`` is
            accepted which indicates a transparent background.
    """
    def invert_row_bits(row):
        """\
        Inverts the row bits 0 -> 1, 1 -> 0
        """
        return bytearray([b ^ 0x1 for b in row])

    def row_to_color_values(row, colours):
        return b''.join(colours[b] for b in row)

    if not dark:
        raise ValueError('Invalid stroke color "{0}"'.format(dark))
    width, height, border = _valid_width_height_and_border(version, scale, border)
    row_iter = matrix_iter(matrix, version, scale, border)
    depth, maxval, tuple_type = 1, 1, 'BLACKANDWHITE'
    transparency = False
    stroke_color = _color_to_rgb_or_rgba(dark, alpha_float=False)
    bg_color = _color_to_rgb_or_rgba(light, alpha_float=False) if light is not None else None
    colored_stroke = not (_color_is_black(stroke_color) or _color_is_white(stroke_color))
    if bg_color is None:
        tuple_type = 'GRAYSCALE_ALPHA' if not colored_stroke else 'RGB_ALPHA'
        transparency = True
        bg_color = _invert_color(stroke_color[:3])
        bg_color += (0,)
        if len(stroke_color) != 4:
            stroke_color += (255,)
    elif colored_stroke or not (_color_is_black(bg_color) or _color_is_white(bg_color)):
        tuple_type = 'RGB'
    is_rgb = tuple_type.startswith('RGB')
    colours = None
    if not is_rgb and transparency:
        depth = 2
        colours = (b'\x01\x00', b'\x00\x01')
    elif is_rgb:
        maxval = max(chain(stroke_color, bg_color))
        depth = 3 if not transparency else 4
        fmt = '>{0}B'.format(depth).encode('ascii')
        colours=(pack(fmt, *bg_color), pack(fmt, *stroke_color))
    row_filter = invert_row_bits if colours is None else partial(row_to_color_values, colours=colours)
    with writable(out, 'wb') as f:
        write = f.write
        write('P7\n'
              '# Created by {0}\n'
              'WIDTH {1}\n'
              'HEIGHT {2}\n'
              'DEPTH {3}\n'
              'MAXVAL {4}\n'
              'TUPLTYPE {5}\n'
              'ENDHDR\n'.format(CREATOR, width, height, depth, maxval, tuple_type).encode('ascii'))
        for row in row_iter:
            write(row_filter(row))


@colorful(dark='#000', light='#fff')
def write_ppm(matrix, version, out, colormap, scale=1, border=None):
    """\
    Serializes the matrix as `PPM <http://netpbm.sourceforge.net/doc/ppm.html>`_
    image.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write binary data.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 pixel per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    """
    scale = int(scale)
    width, height, border = _valid_width_height_and_border(version, scale, border)
    if None in colormap.values():
        raise ValueError('Transparency is not supported')
    for mt, clr in colormap.items():
        colormap[mt] = _color_to_rgb(clr)
    row_iter = matrix_iter_verbose(matrix, version, scale, border)
    with writable(out, 'wb') as f:
        write = f.write
        write('P6 # Created by {0}\n{1} {2} 255\n'
              .format(CREATOR, width, height).encode('ascii'))
        for row in row_iter:
            write(b''.join(pack(b'>3B', *colormap[mt]) for mt in row))


def write_xpm(matrix, version, out, scale=1, border=None, dark='#000',
              light='#fff', name='img'):
    """\
    Serializes the matrix as `XPM <https://en.wikipedia.org/wiki/X_PixMap>`_ image.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write binary data.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 pixel per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param dark: Color of the modules (default: black). The
            color can be provided as ``(R, G, B)`` tuple, as web color name
            (like "red") or in hexadecimal format (``#RGB`` or ``#RRGGBB``).
    :param light: Optional background color (default: white).
            See `color` for valid values. ``None`` indicates a transparent
            background.
    :param str name: Name of the image (must be a valid C-identifier).
            Default: "img".
    """
    width, height, border = _valid_width_height_and_border(version, scale, border)
    row_iter = matrix_iter(matrix, version, scale, border)
    stroke_color = color_to_rgb_hex(dark)
    bg_color = color_to_rgb_hex(light) if light is not None else 'None'
    with writable(out, 'wt') as f:
        write = f.write
        write('/* XPM */\n'
              'static char *{0}[] = {{\n'
              '"{1} {2} 2 1",\n'
              '"  c {3}",\n'
              '"X c {4}",\n'.format(name, width, height, bg_color, stroke_color))
        for i, row in enumerate(row_iter):
            write(''.join(chain(['"'],  (' ' if not b else 'X' for b in row),
                                ['"{0}\n'.format(',' if i < height - 1 else '')])))
        write('};\n')


def write_xbm(matrix, version, out, scale=1, border=None, name='img'):
    """\
    Serializes the matrix as `XBM <https://en.wikipedia.org/wiki/X_BitMap>`_ image.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write text data.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 in the provided unit per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param name: Prefix for the variable names. Default: "img".
                 The prefix is used to construct the variable names:
                 ```#define <prefix>_width``` ```static unsigned char <prefix>_bits[]```
    """
    width, height, border = _valid_width_height_and_border(version, scale, border)
    row_iter = matrix_iter(matrix, version, scale, border)
    with writable(out, 'wt') as f:
        write = f.write
        write('#define {0}_width {1}\n'
              '#define {0}_height {2}\n'
              'static unsigned char {0}_bits[] = {{\n'.format(name, width, height))
        for i, row in enumerate(row_iter, start=1):
            iter_ = zip_longest(*[iter(row)] * 8, fillvalue=0x0)
            # Reverse bits since XBM uses little endian
            bits = ['0x{0:02x}'.format(reduce(lambda x, y: (x << 1) + y, bits[::-1])) for bits in iter_]
            write('    ')
            write(', '.join(bits))
            write(',\n' if i < height else '\n')
        write('};\n')


def write_tex(matrix, version, out, scale=1, border=None, dark='black', unit='pt', url=None):
    """\
    Serializes the matrix as LaTeX PGF picture.

    Requires the `PGF/TikZ <https://en.wikipedia.org/wiki/PGF/TikZ>`_ package
    (i.e. ``\\usepackage{pgf}``) in the LaTeX source.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: Filename or a file-like object supporting to write text data.
    :param scale: Indicates the size of a single module (default: 1 which
            corresponds to 1 x 1 in the provided unit per module).
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    :param str dark: LaTeX color name. The color name is taken at it is, so
            ensure that it refers either to a default color name or that the
            color was defined previously.
    :param unit: Unit of the drawing (default: ``pt``)
    :param url: Optional URL where the QR Code should point to. Requires the
            "hyperref" package. Default: ``None``.
    """
    def point(x, y):
        return '\\pgfqpoint{{{0}{2}}}{{{1}{2}}}'.format(x, y, unit)

    check_valid_scale(scale)
    check_valid_border(border)
    border = get_border(version, border)
    with writable(out, 'wt') as f:
        write = f.write
        write('% Creator:  {0}\n'.format(CREATOR))
        write('% Date:     {0}\n'.format(time.strftime('%Y-%m-%dT%H:%M:%S')))
        if url:
            write('\\href{{{0}}}{{'.format(url))
        write('\\begin{pgfpicture}\n')
        write('  \\pgfsetlinewidth{{{0}{1}}}\n'.format(scale, unit))
        if dark and dark != 'black':
            write('  \\color{{{0}}}\n'.format(dark))
        x, y = border, -border
        for (x1, y1), (x2, y2) in matrix_to_lines(matrix, x, y, incby=-1):
            write('  \\pgfpathmoveto{{{0}}}\n'.format(point(x1 * scale, y1 * scale)))
            write('  \\pgfpathlineto{{{0}}}\n'.format(point(x2 * scale, y2 * scale)))
        write('  \\pgfusepath{stroke}\n')
        write('\\end{{pgfpicture}}{0}\n'.format('' if not url else '}'))


def write_terminal(matrix, version, out, border=None):
    """\
    Function to write to a terminal which supports ANSI escape codes.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version.
    :param out: Filename or a file-like object supporting to write text.
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    """
    with writable(out, 'wt') as f:
        write = f.write
        colours = ['\033[{0}m'.format(i) for i in (7, 49)]
        for row in matrix_iter(matrix, version, scale=1, border=border):
            prev_bit = -1
            cnt = 0
            for bit in row:
                if bit == prev_bit:
                    cnt += 1
                else:
                    if cnt:
                        write(colours[prev_bit])
                        write('  ' * cnt)
                        write('\033[0m')  # reset color
                    prev_bit = bit
                    cnt = 1
            if cnt:
                write(colours[prev_bit])
                write('  ' * cnt)
                write('\033[0m')  # reset color
            write('\n')


def write_terminal_win(matrix, version, border=None):  # pragma: no cover
    """\
    Function to write a QR Code to a MS Windows terminal.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param int border: Integer indicating the size of the quiet zone.
            If set to ``None`` (default), the recommended border size
            will be used (``4`` for QR Codes, ``2`` for a Micro QR Codes).
    """
    import sys
    import struct
    import ctypes
    write = sys.stdout.write
    std_out = ctypes.windll.kernel32.GetStdHandle(-11)
    csbi = ctypes.create_string_buffer(22)
    res = ctypes.windll.kernel32.GetConsoleScreenBufferInfo(std_out, csbi)
    if not res:
        raise OSError('Cannot find information about the console. '
                      'Not running on the command line?')
    default_color = struct.unpack(b'hhhhHhhhhhh', csbi.raw)[4]
    set_color = partial(ctypes.windll.kernel32.SetConsoleTextAttribute, std_out)
    colours = (240, default_color)
    for row in matrix_iter(matrix, version, scale=1, border=border):
        prev_bit = -1
        cnt = 0
        for bit in row:
            if bit == prev_bit:
                cnt += 1
            else:
                if cnt:
                    set_color(colours[prev_bit])
                    write('  ' * cnt)
                prev_bit = bit
                cnt = 1
        if cnt:
            set_color(colours[prev_bit])
            write('  ' * cnt)
        set_color(default_color)  # reset color
        write('\n')


def _color_to_rgb_or_rgba(color, alpha_float=True):
    """\
    Returns the provided color as ``(R, G, B)`` or ``(R, G, B, A)`` tuple.

    If the alpha value is opaque, an RGB tuple is returned, otherwise an RGBA
    tuple.

    :param color: A web color name (i.e. ``darkblue``) or a hexadecimal value
            (``#RGB`` or ``#RRGGBB``) or a RGB(A) tuple (i.e. ``(R, G, B)`` or
            ``(R, G, B, A)``)
    :param bool alpha_float: Indicates if the alpha value should be returned as
            float value. If ``False``, the alpha value is an integer value in
            the range of ``0 .. 254``.
    :rtype: tuple
    """
    rgba = _color_to_rgba(color, alpha_float=alpha_float)
    if rgba[3] in (1.0, 255):
        return rgba[:3]
    return rgba


def _color_to_webcolor(color, allow_css3_colors=True, optimize=True):
    """\
    Returns either a hexadecimal code or a color name.

    :param color: A web color name (i.e. ``darkblue``) or a hexadecimal value
            (``#RGB`` or ``#RRGGBB``) or a RGB(A) tuple (i.e. ``(R, G, B)`` or
            ``(R, G, B, A)``)
    :param bool allow_css3_colors: Indicates if a CSS3 color value like
            rgba(R G, B, A) is an acceptable result.
    :param bool optimize: Inidcates if the shortest possible color value should
            be returned (default: ``True``).
    :rtype: str
    :return: The provided color as web color: ``#RGB``, ``#RRGGBB``,
            ``rgba(R, G, B, A)``, or web color name.
    """
    if _color_is_black(color):
        return '#000'
    elif _color_is_white(color):
        return '#fff'
    clr = _color_to_rgb_or_rgba(color)
    alpha_channel = None
    if len(clr) == 4:
        if allow_css3_colors:
            return 'rgba({0},{1},{2},{3})'.format(*clr)
        alpha_channel = clr[3]
        clr = clr[:3]
    hx = '#{0:02x}{1:02x}{2:02x}'.format(*clr)
    if optimize:
        if hx == '#d2b48c':
            hx = 'tan'  # shorter
        elif hx == '#ff0000':
            hx = 'red'  # shorter
        elif hx[1] == hx[2] and hx[3] == hx[4] and hx[5] == hx[6]:
            hx = '#{0}{1}{2}'.format(hx[1], hx[3], hx[5])
    return hx if alpha_channel is None else (hx, alpha_channel)


def color_to_rgb_hex(color):
    """\
    Returns the provided color in hexadecimal representation.

    :param color: A web color name (i.e. ``darkblue``) or a hexadecimal value
            (``#RGB`` or ``#RRGGBB``) or a RGB(A) tuple (i.e. ``(R, G, B)`` or
            ``(R, G, B, A)``)
    :returns: ``#RRGGBB``.
    """
    return '#{0:02x}{1:02x}{2:02x}'.format(*_color_to_rgb(color))


def _color_is_black(color):
    """\
    Returns if the provided color represents "black".

    :param color: A web color name (i.e. ``darkblue``) or a hexadecimal value
            (``#RGB`` or ``#RRGGBB``) or a RGB(A) tuple (i.e. ``(R, G, B)`` or
            ``(R, G, B, A)``)
    :return: ``True`` if color is represents black, otherwise ``False``.
    """
    try:
        color = color.lower()
    except AttributeError:
        pass
    return color in ('#000', '#000000', 'black', (0, 0, 0), (0, 0, 0, 255),
                     (0, 0, 0, 1.0))


def _color_is_white(color):
    """\
    Returns if the provided color represents "black".

    :param color: A web color name (i.e. ``darkblue``) or a hexadecimal value
            (``#RGB`` or ``#RRGGBB``) or a RGB(A) tuple (i.e. ``(R, G, B)`` or
            ``(R, G, B, A)``)
    :return: ``True`` if color is represents white, otherwise ``False``.
    """
    try:
        color = color.lower()
    except AttributeError:
        pass
    return color in ('#fff', '#ffffff', 'white', (255, 255, 255),
                     (255, 255, 255, 255), (255, 255, 255, 1.0))


def _color_to_rgb(color):
    """\
    Converts web color names like "red" or hexadecimal values like "#36c",
    "#FFFFFF" and RGB tuples like ``(255, 255 255)`` into a (R, G, B) tuple.

    :param color: A web color name (i.e. ``darkblue``) or a hexadecimal value
            (``#RGB`` or ``#RRGGBB``) or a RGB tuple (i.e. ``(R, G, B)``))
    :return: ``(R, G, B)`` tuple.
    """
    rgb = _color_to_rgb_or_rgba(color)
    if len(rgb) != 3:
        raise ValueError('The alpha channel {0} in color "{1}" cannot be '
                         'converted to RGB'.format(rgb[3], color))
    return rgb


def _color_to_rgba(color, alpha_float=True):
    """\
    Returns a (R, G, B, A) tuple.

    :param color: A web color name (i.e. ``darkblue``) or a hexadecimal value
            (``#RGB`` or ``#RRGGBB``) or a RGB(A) tuple (i.e. ``(R, G, B)`` or
            ``(R, G, B, A)``)
    :param bool alpha_float: Indicates if the alpha value should be returned as
            float value. If ``False``, the alpha value is an integer value in
            the range of ``0 .. 254``.
    :return: ``(R, G, B, A)`` tuple.
    """
    res = []
    alpha_channel = (1.0,) if alpha_float else (255,)
    if isinstance(color, tuple):
        col_length = len(color)
        is_valid = False
        if 3 <= col_length <= 4:
            for i, part in enumerate(color[:3]):
                is_valid = 0 <= part <= 255
                res.append(part)
                if not is_valid or i == 2:
                    break
            if is_valid:
                if col_length == 4:
                    res.append(_alpha_value(color[3], alpha_float))
                else:
                    res.append(alpha_channel[0])
        if is_valid:
            return tuple(res)
        raise ValueError('Unsupported color "{0}"'.format(color))
    try:
        return _NAME2RGB[color.lower()] + alpha_channel
    except KeyError:
        try:
            clr = _hex_to_rgb_or_rgba(color, alpha_float=alpha_float)
            if len(clr) == 4:
                return clr
            else:
                return clr + alpha_channel
        except ValueError:
            raise ValueError('Unsupported color "{0}". Neither a known web '
                             'color name nor a color in hexadecimal format.'
                             .format(color))


def _hex_to_rgb_or_rgba(color, alpha_float=True):
    """\
    Helper function to convert a color provided in hexadecimal format (``#RGB``
    or ``#RRGGBB``) to a RGB(A) tuple.

    :param str color: Hexadecimal color name.
    :param bool alpha_float: Indicates if the alpha value should be returned as
            float value. If ``False``, the alpha value is an integer value in
            the range of ``0 .. 254``.
    :return: Tuple of integer values representing a RGB(A) color.
    :rtype: tuple
    :raises: :py:exc:`ValueError` in case the provided string could not
                converted into a RGB(A) tuple
    """
    if color[0] == '#':
        color = color[1:]
    if 2 < len(color) < 5:
        # Expand RGB -> RRGGBB and RGBA -> RRGGBBAA
        color = ''.join([color[i] * 2 for i in range(len(color))])
    color_len = len(color)
    if color_len not in (6, 8):
        raise ValueError('Input #{0} is not in #RRGGBB nor in #RRGGBBAA format'.format(color))
    res = tuple([int(color[i:i+2], 16) for i in range(0, color_len, 2)])
    if alpha_float and color_len == 8:
        res = res[:3] + (_alpha_value(res[3], alpha_float),)
    return res


_ALPHA_COMMONS = {255: 1.0, 128: .5, 64: .25, 32: .125, 16: .625, 0: 0.0}

def _alpha_value(color, alpha_float):
    if alpha_float:
        if not isinstance(color, float):
            if 0 <= color <= 255:
                return _ALPHA_COMMONS.get(color, float('%.02f' % (color / 255.0)))
        else:
            if 0 <= color <= 1.0:
                return color
    else:
        if not isinstance(color, float):
            if 0 <= color <= 255:
                return color
        else:
            if 0 <= color <= 1.0:
                return color * 255.0
    raise ValueError('Invalid alpha channel value: {0}'.format(color))


def _invert_color(rgb_or_rgba):
    """\
    Returns the inverse color for the provided color.

    This function does not check if the color is a valid RGB / RGBA color.

    :param rgb: (R, G, B) or (R, G, B, A) tuple.
    """
    return tuple([255 - c for c in rgb_or_rgba])


# <http://www.w3.org/TR/css3-color/#svg-color>
_NAME2RGB = {
    'aliceblue': (240, 248, 255),
    'antiquewhite': (250, 235, 215),
    'aqua': (0, 255, 255),
    'aquamarine': (127, 255, 212),
    'azure': (240, 255, 255),
    'beige': (245, 245, 220),
    'bisque': (255, 228, 196),
    'black': (0, 0, 0),
    'blanchedalmond': (255, 235, 205),
    'blue': (0, 0, 255),
    'blueviolet': (138, 43, 226),
    'brown': (165, 42, 42),
    'burlywood': (222, 184, 135),
    'cadetblue': (95, 158, 160),
    'chartreuse': (127, 255, 0),
    'chocolate': (210, 105, 30),
    'coral': (255, 127, 80),
    'cornflowerblue': (100, 149, 237),
    'cornsilk': (255, 248, 220),
    'crimson': (220, 20, 60),
    'cyan': (0, 255, 255),
    'darkblue': (0, 0, 139),
    'darkcyan': (0, 139, 139),
    'darkgoldenrod': (184, 134, 11),
    'darkgray': (169, 169, 169),
    'darkgreen': (0, 100, 0),
    'darkgrey': (169, 169, 169),
    'darkkhaki': (189, 183, 107),
    'darkmagenta': (139, 0, 139),
    'darkolivegreen': (85, 107, 47),
    'darkorange': (255, 140, 0),
    'darkorchid': (153, 50, 204),
    'darkred': (139, 0, 0),
    'darksalmon': (233, 150, 122),
    'darkseagreen': (143, 188, 143),
    'darkslateblue': (72, 61, 139),
    'darkslategray': (47, 79, 79),
    'darkslategrey': (47, 79, 79),
    'darkturquoise': (0, 206, 209),
    'darkviolet': (148, 0, 211),
    'deeppink': (255, 20, 147),
    'deepskyblue': (0, 191, 255),
    'dimgray': (105, 105, 105),
    'dimgrey': (105, 105, 105),
    'dodgerblue': (30, 144, 255),
    'firebrick': (178, 34, 34),
    'floralwhite': (255, 250, 240),
    'forestgreen': (34, 139, 34),
    'fuchsia': (255, 0, 255),
    'gainsboro': (220, 220, 220),
    'ghostwhite': (248, 248, 255),
    'gold': (255, 215, 0),
    'goldenrod': (218, 165, 32),
    'gray': (128, 128, 128),
    'green': (0, 128, 0),
    'greenyellow': (173, 255, 47),
    'grey': (128, 128, 128),
    'honeydew': (240, 255, 240),
    'hotpink': (255, 105, 180),
    'indianred': (205, 92, 92),
    'indigo': (75, 0, 130),
    'ivory': (255, 255, 240),
    'khaki': (240, 230, 140),
    'lavender': (230, 230, 250),
    'lavenderblush': (255, 240, 245),
    'lawngreen': (124, 252, 0),
    'lemonchiffon': (255, 250, 205),
    'lightblue': (173, 216, 230),
    'lightcoral': (240, 128, 128),
    'lightcyan': (224, 255, 255),
    'lightgoldenrodyellow': (250, 250, 210),
    'lightgray': (211, 211, 211),
    'lightgreen': (144, 238, 144),
    'lightgrey': (211, 211, 211),
    'lightpink': (255, 182, 193),
    'lightsalmon': (255, 160, 122),
    'lightseagreen': (32, 178, 170),
    'lightskyblue': (135, 206, 250),
    'lightslategray': (119, 136, 153),
    'lightslategrey': (119, 136, 153),
    'lightsteelblue': (176, 196, 222),
    'lightyellow': (255, 255, 224),
    'lime': (0, 255, 0),
    'limegreen': (50, 205, 50),
    'linen': (250, 240, 230),
    'magenta': (255, 0, 255),
    'maroon': (128, 0, 0),
    'mediumaquamarine': (102, 205, 170),
    'mediumblue': (0, 0, 205),
    'mediumorchid': (186, 85, 211),
    'mediumpurple': (147, 112, 219),
    'mediumseagreen': (60, 179, 113),
    'mediumslateblue': (123, 104, 238),
    'mediumspringgreen': (0, 250, 154),
    'mediumturquoise': (72, 209, 204),
    'mediumvioletred': (199, 21, 133),
    'midnightblue': (25, 25, 112),
    'mintcream': (245, 255, 250),
    'mistyrose': (255, 228, 225),
    'moccasin': (255, 228, 181),
    'navajowhite': (255, 222, 173),
    'navy': (0, 0, 128),
    'oldlace': (253, 245, 230),
    'olive': (128, 128, 0),
    'olivedrab': (107, 142, 35),
    'orange': (255, 165, 0),
    'orangered': (255, 69, 0),
    'orchid': (218, 112, 214),
    'palegoldenrod': (238, 232, 170),
    'palegreen': (152, 251, 152),
    'paleturquoise': (175, 238, 238),
    'palevioletred': (219, 112, 147),
    'papayawhip': (255, 239, 213),
    'peachpuff': (255, 218, 185),
    'peru': (205, 133, 63),
    'pink': (255, 192, 203),
    'plum': (221, 160, 221),
    'powderblue': (176, 224, 230),
    'purple': (128, 0, 128),
    'red': (255, 0, 0),
    'rosybrown': (188, 143, 143),
    'royalblue': (65, 105, 225),
    'saddlebrown': (139, 69, 19),
    'salmon': (250, 128, 114),
    'sandybrown': (244, 164, 96),
    'seagreen': (46, 139, 87),
    'seashell': (255, 245, 238),
    'sienna': (160, 82, 45),
    'silver': (192, 192, 192),
    'skyblue': (135, 206, 235),
    'slateblue': (106, 90, 205),
    'slategray': (112, 128, 144),
    'slategrey': (112, 128, 144),
    'snow': (255, 250, 250),
    'springgreen': (0, 255, 127),
    'steelblue': (70, 130, 180),
    'tan': (210, 180, 140),
    'teal': (0, 128, 128),
    'thistle': (216, 191, 216),
    'tomato': (255, 99, 71),
    'turquoise': (64, 224, 208),
    'violet': (238, 130, 238),
    'wheat': (245, 222, 179),
    'white': (255, 255, 255),
    'whitesmoke': (245, 245, 245),
    'yellow': (255, 255, 0),
    'yellowgreen': (154, 205, 50),
}


def _make_colormap(version, dark, light,
                   finder_dark=False, finder_light=False,
                   data_dark=False, data_light=False,
                   version_dark=False, version_light=False,
                   format_dark=False, format_light=False,
                   alignment_dark=False, alignment_light=False,
                   timing_dark=False, timing_light=False,
                   separator=False, dark_module=False,
                   quiet_zone=False):
    """\
    Creates and returns a module type -> color map.

    The result can be used for serializers which support more than two colors.

    Examples

    .. code-block:: python

        # All dark modules (data, version, ...) will be dark red, the dark
        # modules of the finder patterns will be blue
        # The light modules will be rendered in the serializer's default color
        # (usually white)
        cm = colormap(dark='darkred', finder_dark='blue')

        # Use the serializer's default colors for dark / light modules
        # (usually black and white) but the dark modules of the timing patterns
        # will be brown
        cm = colormap(timing_dark=(165, 42, 42))

    :param version: QR Code version (int constant)
    :param dark: Default color of dark modules
    :param light: Default color of light modules
    :param finder_dark: Color of the dark modules of the finder patterns.
    :param finder_light: Color of the light modules of the finder patterns.
    :param data_dark: Color of the dark data modules.
    :param data_light: Color of the light data modules.
    :param version_dark: Color of the dark modules of the version information.
    :param version_light: Color of the light modules of the version information.
    :param format_dark: Color of the dark modules of the format information.
    :param format_light: Color of the light modules of the format information.
    :param alignment_dark: Color of the dark modules of the alignment patterns.
    :param alignment_light: Color of the light modules of the alignment patterns.
    :param timing_dark: Color of the dark modules of the timing patterns.
    :param timing_light: Color of the light modules of the timing patterns.
    :param separator: Color of the separator.
    :param dark_module: Color of the dark module.
    :param quiet_zone: Color of the quiet zone / border.
    :rtype: dict
    """
    unsupported = ()
    if version < 7:
        unsupported = [consts.TYPE_VERSION_DARK, consts.TYPE_VERSION_LIGHT]
        if version < 1:  # Micro QR Code
            unsupported.extend([consts.TYPE_DARKMODULE,
                                consts.TYPE_ALIGNMENT_PATTERN_DARK,
                                consts.TYPE_ALIGNMENT_PATTERN_LIGHT])
    mt2color = {
        consts.TYPE_FINDER_PATTERN_DARK: finder_dark if finder_dark is not False else dark,
        consts.TYPE_FINDER_PATTERN_LIGHT: finder_light if finder_light is not False else light,
        consts.TYPE_DATA_DARK: data_dark if data_dark is not False else dark,
        consts.TYPE_DATA_LIGHT: data_light if data_light is not False else light,
        consts.TYPE_VERSION_DARK: version_dark if version_dark is not False else dark,
        consts.TYPE_VERSION_LIGHT: version_light if version_light is not False else light,
        consts.TYPE_ALIGNMENT_PATTERN_DARK: alignment_dark if alignment_dark is not False else dark,
        consts.TYPE_ALIGNMENT_PATTERN_LIGHT: alignment_light if alignment_light is not False else light,
        consts.TYPE_TIMING_DARK: timing_dark if timing_dark is not False else dark,
        consts.TYPE_TIMING_LIGHT: timing_light if timing_light is not False else light,
        consts.TYPE_FORMAT_DARK: format_dark if format_dark is not False else dark,
        consts.TYPE_FORMAT_LIGHT: format_light if format_light is not False else light,
        consts.TYPE_SEPARATOR: separator if separator is not False else light,
        consts.TYPE_DARKMODULE: dark_module if dark_module is not False else dark,
        consts.TYPE_QUIET_ZONE: quiet_zone if quiet_zone is not False else light,
    }
    return {mt: val for mt, val in mt2color.items() if mt not in unsupported}


_VALID_SERIALIZERS = {
    'svg': write_svg,
    'png': write_png,
    'eps': write_eps,
    'txt': write_txt,
    'pdf': write_pdf,
    'ans': write_terminal,
    'pbm': write_pbm,
    'pam': write_pam,
    'ppm': write_ppm,
    'tex': write_tex,
    'xbm': write_xbm,
    'xpm': write_xpm,
}


def save(matrix, version, out, kind=None, **kw):
    """\
    Serializes the matrix in any of the supported formats.

    :param matrix: The matrix to serialize.
    :param int version: The (Micro) QR code version
    :param out: A filename or a writable file-like object with a
            ``name`` attribute. If a stream like :py:class:`io.ByteIO` or
            :py:class:`io.StringIO` object without a ``name`` attribute is
            provided, use the `kind` parameter to specify the serialization
            format.
    :param kind: If the desired output format cannot be extracted from
            the filename, this parameter can be used to indicate the
            serialization format (i.e. "svg" to enforce SVG output)
    :param kw: Any of the supported keywords by the specific serialization
            method.
    """
    is_stream = False
    if kind is None:
        try:
            fname = out.name
            is_stream = True
        except AttributeError:
            fname = out
        ext = fname[fname.rfind('.') + 1:].lower()
    else:
        ext = kind.lower()
    is_svgz = not is_stream and ext == 'svgz'
    try:
        serializer = _VALID_SERIALIZERS[ext if not is_svgz else 'svg']
    except KeyError:
        raise ValueError('Unknown file extension ".{0}"'.format(ext))
    if is_svgz:
        with gzip.open(out, 'wb', compresslevel=kw.pop('compresslevel', 9)) as f:
            serializer(matrix, version, f, **kw)
    else:
        serializer(matrix, version, out, **kw)