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#
# 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
"""
Base module for rendering barcodes for Inkscape.
"""
import itertools
import sys
from lxml import etree
(WHITE_BAR, BLACK_BAR, TALL_BAR) = range(3)
TEXT_TEMPLATE = 'font-size:%dpx;text-align:center;text-anchor:middle;'
class Barcode(object):
"""Provide a base class for all barcode renderers"""
name = None
def error(self, bar, msg):
"""Cause an error to be reported"""
sys.stderr.write(
"Error encoding '%s' as %s barcode: %s\n" % (bar, self.name, msg))
return "ERROR"
def __init__(self, param={}):
self.document = param.get('document', None)
self.x = int(param.get('x', 0))
self.y = int(param.get('y', 0))
self.scale = param.get('scale', 1)
self.height = param.get('height', 30)
self.label = param.get('text', None)
self.string = self.encode( self.label )
if not self.string:
return
self.width = len(self.string)
self.data = self.graphicalArray(self.string)
def get_id(self):
"""Get the next useful id"""
if not self.document:
return "barcode"
doc_ids = {}
docIdNodes = self.document.xpath('//@id')
for m in docIdNodes:
doc_ids[m] = 1
name = 'barcode'
index = 0
while (doc_ids.has_key(name)):
index += 1
name = 'barcode%d' % index
return name
def generate(self):
"""Generate the actual svg from the coding"""
svg_uri = u'http://www.w3.org/2000/svg'
if self.string == 'ERROR':
return
if not self.string or not self.data:
raise ValueError("No string specified for barcode.")
data = self.data
name = self.get_id()
# use an svg group element to contain the barcode
barcode = etree.Element('{%s}%s' % (svg_uri,'g'))
barcode.set('id', name)
barcode.set('style', 'fill: black;')
barcode.set('transform', 'translate(%d,%d) scale(%f)' % (self.x, self.y, self.scale))
bar_offset = 0
bar_id = 1
for datum in data:
# Datum 0 tells us what style of bar is to come next
style = self.getStyle(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']:
rect = etree.SubElement(barcode,'{%s}%s' % (svg_uri,'rect'))
rect.set('x', str(bar_offset))
rect.set('y', str(style['top']))
rect.set('width', str(width))
rect.set('height', str(style['height']))
rect.set('id', "%s_bar%d" % (name, bar_id))
bar_offset += width
bar_id += 1
bar_width = bar_offset
# Add text at the bottom of the barcode
text = etree.SubElement(barcode,'{%s}%s' % (svg_uri,'text'))
text.set( 'x', str(int(bar_width / 2)))
text.set( 'y', str(self.height + self.fontSize() ))
text.set( 'style', TEXT_TEMPLATE % self.fontSize() )
text.set( '{http://www.w3.org/XML/1998/namespace}space', 'preserve' )
text.set( 'id', '%s_text' % name )
text.text = str(self.label)
return barcode
def graphicalArray(self, code):
"""Converts black and white markets into a space array"""
return [(x,len(list(y))) for x, y in itertools.groupby(code)]
def getStyle(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.fontSize() / 2)
if index == WHITE_BAR:
result['write'] = False
return result
def fontSize(self):
"""Return the ideal font size, defaults to 9px"""
return 9
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