inkscape/share/extensions/barcode/Base.py

# coding=utf-8
#
# Copyright (C) 2010 Martin Owens
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110, USA.
#
"""
Base module for rendering barcodes for Inkscape.
"""

import itertools
import sys

from inkex import Group, TextElement, Rectangle
from inkex.localization import inkex_gettext as _

(TEXT_POS_BOTTOM, TEXT_POS_TOP) = range(2)
(WHITE_BAR, BLACK_BAR, TALL_BAR) = range(3)
TEXT_TEMPLATE = "font-size:%dpx;text-align:center;text-anchor:middle;"

try:
    from typing import Optional
except ImportError:
    pass


class Barcode(object):
    """Provide a base class for all barcode renderers"""

    default_height = 30
    font_size = 9
    name = None  # type: Optional[str]

    def error(self, text, msg):
        """Cause an error to be reported"""
        sys.stderr.write(
            _("Error encoding '{}' as {} barcode: {}\n").format(text, self.name, msg)
        )
        return "ERROR"

    def encode(self, text):
        """
        Replace this with the encoding function, it should return
        a string of ones and zeros
        """
        raise NotImplementedError("You need to write an encode() function.")

    def __init__(self, param):
        param = param or {}
        self.document = param.get("document", None)
        self.known_ids = []
        self._extra = []

        self.pos_x = int(param.get("x", 0))
        self.pos_y = int(param.get("y", 0))
        self.text = param.get("text", None)
        self.scale = param.get("scale", 1)
        self.height = param.get("height", self.default_height)
        self.pos_text = param.get("text_pos", TEXT_POS_BOTTOM)

        if self.document:
            self.known_ids = list(self.document.xpath("//@id"))

        if not self.text:
            raise ValueError(_("No string specified for barcode."))

    def get_id(self, name="element"):
        """Get the next useful id (and claim it)"""
        index = 0
        while name in self.known_ids:
            index += 1
            name = "barcode{:d}".format(index)
        self.known_ids.append(name)
        return name

    def add_extra_barcode(self, barcode, **kw):
        """Add an extra barcode along side this one, used for ean13 extras"""
        from . import get_barcode

        kw["height"] = self.height
        kw["document"] = self.document
        kw["scale"] = None
        self._extra.append(get_barcode(barcode, **kw).generate())

    def generate(self):
        """Generate the actual svg from the coding"""
        string = self.encode(self.text)

        if string == "ERROR":
            return

        name = self.get_id("barcode")

        # use an svg group element to contain the barcode
        barcode = Group()
        barcode.set("id", name)
        barcode.set("style", "fill: black;")

        barcode.transform.add_translate(self.pos_x, self.pos_y)
        if self.scale:
            barcode.transform.add_scale(self.scale)

        bar_id = 1
        bar_offset = 0
        tops = set()

        for datum in self.graphical_array(string):
            # Datum 0 tells us what style of bar is to come next
            style = self.get_style(int(datum[0]))
            # Datum 1 tells us what width in units,
            # style tells us how wide a unit is
            width = int(datum[1]) * int(style["width"])

            if style["write"]:
                tops.add(style["top"])
                rect = Rectangle()
                rect.set("x", str(bar_offset))
                rect.set("y", str(style["top"]))
                if self.pos_text == TEXT_POS_TOP:
                    rect.set("y", str(style["top"] + self.font_size))
                rect.set("id", "{}_bar{:d}".format(name, bar_id))
                rect.set("width", str(width))
                rect.set("height", str(style["height"]))
                barcode.append(rect)
            bar_offset += width
            bar_id += 1

        for extra in self._extra:
            if extra is not None:
                barcode.append(extra)

        bar_width = bar_offset
        # Add text at the bottom of the barcode
        text = TextElement()
        text.set("x", str(int(bar_width / 2)))
        text.set("y", str(min(tops) + self.font_size - 1))
        if self.pos_text == TEXT_POS_BOTTOM:
            text.set("y", str(self.height + max(tops) + self.font_size))
        text.set("style", TEXT_TEMPLATE % self.font_size)
        text.set("xml:space", "preserve")
        text.set("id", "{}_text".format(name))
        text.text = str(self.text)
        barcode.append(text)
        return barcode

    def graphical_array(self, code):
        """Converts black and white markets into a space array"""
        return [(x, len(list(y))) for x, y in itertools.groupby(code)]

    def get_style(self, index):
        """Returns the styles that should be applied to each bar"""
        result = {"width": 1, "top": 0, "write": True}
        if index == BLACK_BAR:
            result["height"] = int(self.height)
        if index == TALL_BAR:
            result["height"] = int(self.height) + int(self.font_size / 2)
        if index == WHITE_BAR:
            result["write"] = False
        return result