render svg to seperate files

gistfile1.py

import sys

import cairo
import rsvg

from ctypes import *

c_rsvg = CDLL('librsvg-2.so.2')

if len(sys.argv) < 2:
    print "usage: filename.svg [css-selector [css-selector [...]]]"
    print "if css-selector isnt passed then all top level groups will be exported"
    sys.exit(1)

fn = sys.argv[1]
selector = ','.join(sys.argv[2:]) if len(sys.argv) > 2 else '>svg|g'

from lxml import etree
from lxml.cssselect import CSSSelector
sel = CSSSelector(selector, namespaces={'svg':'http://www.w3.org/2000/svg'})

svg = etree.parse(open(fn)).getroot()

groups = sel(svg)

class RsvgPositionData(Structure):
    _fields_ = [("x", c_int),
                ("y", c_int)]

class RsvgDimensionData(Structure):
    _fields_ = [("width", c_int),
                ("height", c_int),
                ("em",c_double),
                ("ex",c_double)]


# regular rsvg handle to draw the svg for cairo
handle_py = rsvg.Handle(None, etree.tostring(svg))

error = ''
# ctypes rsvg handle so we can get element sizes/positions
handle = c_rsvg.rsvg_handle_new_from_file(fn, error)

for group in groups:
    if 'id' not in group.attrib:
        print "skipping element because it has no id"
        continue

    gid = '#'+group.attrib['id']
    out_fn = group.attrib['id'] + '.png'

    # grab the posisiton and size of the element
    p = RsvgPositionData()
    d = RsvgDimensionData()
    c_rsvg.rsvg_handle_get_position_sub(handle, byref(p), gid)
    c_rsvg.rsvg_handle_get_dimensions_sub(handle, byref(d), gid)

    print gid, '-->', out_fn #, p.x, p.y, d.width, d.height, d.em, d.ex

    # create a new surface the correct size ( +1 for a reason im not sure of... )
    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, d.width+1, d.height+1)
    ctx = cairo.Context(surface)
    # "undo" the translation of the element 
    ctx.translate(-p.x, -p.y)
    # draw the element at effectivly 0, 0
    handle_py.render_cairo(ctx, id=gid)

    surface.write_to_png(out_fn)