View source for Creating an Inkscape Effect with Python & ElementTree

[[Category: Cookbook]] [[Category: Python]] [[Category: XML]] [[Category: ElementTree]]

[[Inkscape]]

See also: [[Using argparse to create useful commandline scripts in Python]]

From the [http://wiki.inkscape.org/wiki/index.php/Script_extensions Inkscape wiki]:
 
 (interpreter)? your_script (--param=value)* /path/to/input[[/SVGfile]] | inkscape


== Inkscape Effects: Hello World ==

To create/install an inkscape extension, you need to place it in the Inkscape extensions folder ($HOME/.config/inkscape/extensions/ or /usr/share/inkscape/extensions).

First thing you need is an "inx" file, an "inkscape-extension" XML file that describes your extension to Inkscape. This is pretty much the simplest form of an effect: NB The "submenu" item selects which Menu your effect will be presented under (in this case, we create a new menu called "Python"), and the "_name" element sets the name of the Effect itself.

helloworld.inx
<source lang="xml">
<?xml version="1.0" encoding="UTF-8"?>
<inkscape-extension xmlns="http://www.inkscape.org/namespace/inkscape/extension">
	<_name>Hello World</_name>
	<id>pzi.helloworld</id>
	<dependency type="executable" location="extensions">helloworld.py</dependency>
    <effect>
        <object-type>all</object-type>
        <effects-menu>
            <submenu _name="Python"/>
        </effects-menu>
    </effect>
    <script>
    	<command reldir="extensions" interpreter="python">helloworld.py</command>
    </script>
</inkscape-extension>
</source>

Inkscape reads the inx files when it starts, so Inkscape needs to be restarted when an inx file is added or changed. Luckily, changes to the script do not require that Inkscape get restarted.

Now, for some code, a "Hello World", that does nothing (yet)...

helloworld.py
<source lang="python">
import sys, codecs
from lxml import etree

f = codecs.open(sys.argv[-1], encoding="utf-8")
doc = etree.parse(f)
sys.stdout.write(etree.tostring(doc, encoding="utf-8", xml_declaration=True))
</source>

helloworld.py (with log)
<source lang="python">
import sys, codecs
from lxml import etree

log = open("helloworld.log", "w")
log.write("argv: " + str(sys.argv))
log.close()

f = codecs.open(sys.argv[-1], encoding="utf-8")
doc = etree.parse(f)
sys.stdout.write(etree.tostring(doc, encoding="utf-8", xml_declaration=True))
</source>

helloworld.py, reading minimal arguments from inkscape

<source lang="python">
import sys, codecs, argparse
from lxml import etree

parser = argparse.ArgumentParser(description="My first Inkscape effect")
parser.add_argument('--id', action="append", help="id(s) of selected elements")
parser.add_argument('path', help="path of svg file to open")

args = parser.parse_args()

f = codecs.open(args.path, encoding="utf-8")
doc = etree.parse(f)
sys.stdout.write(etree.tostring(doc, encoding="utf-8", xml_declaration=True))
</source>

Finally, a version that uses etree to modify the fill of path elements.

<source lang="python">
import sys, codecs, argparse
from lxml import etree

NS = { 'svg':"http://www.w3.org/2000/svg" }

parser = argparse.ArgumentParser(description="My first Inkscape effect")
parser.add_argument('--id', action="append", help="id(s) of selected elements")
parser.add_argument('path', help="path of svg file to open")

args = parser.parse_args()

# Open the file & parse to a "etree" object
f = codecs.open(args.path, encoding="utf-8")
t = etree.parse(f)

# Loop over all svg:path elements
for path in t.xpath("//svg:path", namespaces=NS):
    style = path.get("style")
    if style:
        path.set("style", style.replace("fill:none", "fill:#FF0000"))

# Output the (modified) tree
sys.stdout.write(etree.tostring(doc, encoding="utf-8", xml_declaration=True))
</source>

Example Inkscape filter, manipulating the SVG as text with search and replace:

<source lang="python">
import sys, codecs
from lxml import etree
 
# open the filename given on the commandline
f = codecs.open(sys.argv[-1], encoding="utf-8")
text = f.read()

text = text.replace("FOO", "this is some magic value")

# OUTPUT THE TREE
print text

</source>

Example showing 3 different kinds of manipulations:
<source lang="python">
import sys, codecs, argparse
from lxml import etree

NS = { 'svg':"http://www.w3.org/2000/svg" }

parser = argparse.ArgumentParser(description="My first Inkscape effect")
parser.add_argument('--id', action="append", help="id(s) of selected elements")
parser.add_argument('path', help="path of svg file to open")

args = parser.parse_args()

# Open the file & parse to a "etree" object
f = codecs.open(args.path, encoding="utf-8")
t = etree.parse(f)

# I. Select and alter existing elements
#
# Loop over all svg:path elements
for path in t.xpath("//svg:path ", namespaces=NS):
    style = path.get("style")
    if style:
        path.set("style", style.replace("fill:none", "fill:#FFFF00"))

## II. Create & Insert a new element
## l.append(thing)
## l.insert(index, thing)
r = etree.Element("rect")
r.attrib['x'] = "100"
r.attrib['y'] = "100"
r.attrib['width'] = "50"
r.attrib['height'] = "50"
r.attrib["style"] = "fill:#00FF00;"
g = t.xpath("//svg:g", namespaces=NS)[0]
g.append(r)


## III: Clone & insert an element
from copy import deepcopy
for id in args.id:
    p = t.xpath("//*[@id='{0}']".format(id))
    if len(p):
        p = p[0]
        p2 = deepcopy(p)
        del p2.attrib["id"]
        p.getparent().append(p2)


# Output the (modified) tree
sys.stdout.write(etree.tostring(t, encoding="utf-8", xml_declaration=True))


</source>

== Resources ==
* http://wiki.inkscape.org/wiki/index.php/Script_extensions
* http://wiki.inkscape.org/wiki/index.php/INX_extension_descriptor_format
* http://wiki.inkscape.org/wiki/index.php/Release_notes/0.47#Extension_API_changes
* http://lxml.de/tutorial.html
* http://www.w3.org/TR/xpath/