Simplify SVGs by applying transform - reduce size

Question

I have quite often some SVGs with structures like this:

<svg:g
  transform="translate(-251.5,36.5)"
  id="g12578"
  style="fill:#ffff00;fill-opacity:1">
  <svg:rect
width="12"
height="12"
x="288"
y="35.999958"
id="rect12580"
style="fill:#ffff00;fill-opacity:1;stroke:#000000;stroke-width:1" />
</svg:g>

I would like to apply translate directly to the coordinates and delete the tranform-attribute:

<svg:g
  id="g12578"
  style="fill:#ffff00;fill-opacity:1">
  <svg:rect
width="12"
height="12"
x="36.5"
y="69.499958"
id="rect12580"
style="fill:#ffff00;fill-opacity:1;stroke:#000000;stroke-width:1" />
</svg:g>

Do you know a script / program for simplifying SVGs? Or a python-snipplet for parsing SVG's?

This script works for my special case, but I would like one which works allways:

#http://epydoc.sourceforge.net/stdlib/xml.dom.minidom.Element-class.html
from xml.dom.minidom import parse, parseString
import re

f = open('/home/moose/mathe/svg/Solitaire-Board.svg', 'r')

xmldoc = parse(f)

p = re.compile('translate\(([-\d.]+),([-\d.]+)\)', re.IGNORECASE)

for node in xmldoc.getElementsByTagName('svg:g'):
  transform_dict = node.attributes["transform"]
  m = p.match(transform_dict.value)
  if m:
    x = float(m.group(1))
    y = float(m.group(2))
  child_rectangles = node.getElementsByTagName('svg:rect') 
  for rectangle in child_rectangles:
    x_dict = rectangle.attributes["x"]
    y_dict = rectangle.attributes["y"]
    new_x = float(x_dict.value) + x
    new_y = float(y_dict.value) + y
    rectangle.setAttribute('x', str(new_x))
    rectangle.setAttribute('y', str(new_y))
  node.removeAttribute('transform')

print xmldoc.toxml()

I think the size of the svg could be reduced quite heavily without loss of quality, if the transform-attribute could be removed. If the tool would be able to reduce coordinate precision, delete unnecessary regions, group and style wisely it would be great.

Answer 1

I'd recommend using lxml. It's extremely fast and has a lot of nice features. You can parse your example if you properly declare the svg namespace prefix. You can do that pretty easily:

>>> svg = '<svg xmlns:svg="http://www.w3.org/2000/svg">' + example_svg + '</svg>'

Now you can parse it with lxml.etree (or xml.etree.ElementTree):

>>> doc = etree.fromstring(svg)

If you use lxml you can take advantage of XPath:

>>> ns = {'svg': 'http://www.w3.org/2000/svg'}

>>> doc.xpath('//svg:g/@transform', namespaces=ns)
<<< ['translate(-251.5,36.5)']