Simple code to create a very clean SVG EAN13 code.

SVG EAN13 creator

class Ean13BarcodeException(Exception):
    pass


class Ean13Barcode(object):
    """Generate a SVG for a given EAN13 code with a specified width and height"""

    def __init__(self, width, height, colorstring='rgb(0,0,0)'):
        self.width = width
        self.height = height
        self.colorstring = colorstring

        self.codes = {
            'A': ['0001101', '0011001', '0010011', '0111101', '0100011',
                  '0110001', '0101111', '0111011', '0110111', '0001011'],
            'B': ['0100111', '0110011', '0011011', '0100001', '0011101',
                  '0111001', '0000101', '0010001', '0001001', '0010111'],
            'C': ['1110010', '1100110', '1101100', '1000010', '1011100',
                  '1001110', '1010000', '1000100', '1001000', '1110100'],
        }

        self.parities = [
            ('A', 'A', 'A', 'A', 'A', 'A'),
            ('A', 'A', 'B', 'A', 'B', 'B'),
            ('A', 'A', 'B', 'B', 'A', 'B'),
            ('A', 'A', 'B', 'B', 'B', 'A'),
            ('A', 'B', 'A', 'A', 'B', 'B'),
            ('A', 'B', 'B', 'A', 'A', 'B'),
            ('A', 'B', 'B', 'B', 'A', 'A'),
            ('A', 'B', 'A', 'B', 'A', 'B'),
            ('A', 'B', 'A', 'B', 'B', 'A'),
            ('A', 'B', 'B', 'A', 'B', 'A')
        ]

    def generate(self, barcode, generate_controldigit=True):
        """the controldigit is the 13th digit which is a checksum. 
           Most likely you want this code to calculate it for you"""
        barcode = str(barcode)

        # Some sanity first.
        if generate_controldigit and len(barcode) > 12:
            raise Ean13BarcodeException('Length already 13 digits, cannot add controldigit')

        if generate_controldigit and len(barcode) <= 12:
            barcode = barcode.rjust(12, '0')
            barcode = "%s%s" % (barcode, self.create_controldigit(barcode))
        elif len(barcode) < 13:
            barcode = barcode.rjust(13, '0')

        if not generate_controldigit and not self.check_controldigit(barcode):
            raise Ean13BarcodeException('Control digit is not correct! (13th digits)')

        # Generate 'bit'-range
        code = ['101']
        p = self.parities[int(barcode[0])]
        for i in range(1, 7):
            code.append(self.codes[p[i-1]][int(barcode[i])])
        code.append('01010')
        for i in range(7, 13):
            code.append(self.codes['C'][int(barcode[i])])
        code.append('101')

        # Create the svg
        return self._svg(self._stack(''.join(code)))

    def _svg(self, stack):
        x = 0
        bars = []
        sbw = self.width / sum(stack)
        for i, e in enumerate(stack):
            w = e * sbw
            if not i % 2: # only 'odd' ones should be painted
                bars.append('<rect width="%s" height="%s" x="%s" y="0" style="fill:%s;"/>' %
                                (w, self.height, x, self.colorstring))
            x += w

        return '<svg width="%s" height="%s">%s</svg>' % (self.width, self.height, "\n".join(bars))

    @staticmethod
    def _stack(bitseries):
        currentbit = '1'
        rv = [0]
        for i in bitseries:
            if i == currentbit:
                rv[len(rv)-1] += 1
            else:
                currentbit = i
                rv.append(1)
        return rv

    @classmethod
    def check_controldigit(cls, code):
        assert(len(code) == 13)
        c = code[0:12]
        r = int(code[12:13])
        return r == cls.create_controldigit(c)

    @classmethod
    def create_controldigit(cls, code):
        assert(len(code) == 12)
        s = 0
        for i in range(1, 12, 2):
            s += 3 * int(code[i])
        for i in range(0, 11, 2):
            s += int(code[i])
        r = s % 10
        if r > 0:
            r = 10 - r
        return r