My first effect extension#



Effect extensions take the svg from Inkscape, modify it in some way and pass the modified version back to Inkscape to be rendered onto the canvas. This can be very powerful, allowing everything from randomising colours to manipulating path elements in external programs.

We are going to write an effect extension that will simply change the fill any selected object to red.

Step One#

Extract the Effect Extension Template files into a folder on your computer. You should have two files, one inx file and one python file. Move or link these files into your extensions directory as you would when installing extensions manually. This is the directory listed at Edit > Preferences > System: User extensions.

Edit the inx file in a text editor and change the name of the extension to Make Red Extension and the id to org.inkscape.tutorial.make_red_extension by changing these lines near the top:

<?xml version="1.0" encoding="UTF-8"?>
<inkscape-extension xmlns="">
  <name>Make Red Extension</name>

Toward the end of the .inx file, change the submenu to Color specify that this extension will be listed in the Color submenu under the Extensions menu:

        <submenu name="Color"/>

Step Two#

Next, open in your text editor. You can see this is an inkex extension because it contains a python class that inherits from inkex.EffectExtension. Change the class name to MakeRedExtension:

class MakeRedExtension(inkex.EffectExtension):

Reflect this change down in the __main__ section of the code by changing the class name to MakeRedExtension there:

if __name__ == '__main__':

When a standard inkex-based python effect extension is run, it will call a method called effect() on your extension’s class. So, most of the code you need to write will go there. Edit‘s effect() method to look like the following, being sure that the indentation is correct so that effect() is recognized as a method of the MakeRedExtension class:

for elem in self.svg.selection:['fill'] = 'red'['fill-opacity'] = 1['opacity'] = 1

Code Explanation#

We want to change the color of all selected objects to red. For this we need to loop through each of the selected paths. The first line of inkex.base.InkscapeExtension.effect() does this. The selection attribute of self.svg contains the currently selected objects.


self.svg contains the SVG document in its current state - passed by Inkscape - and is already parsed for us, so we don’t have to manipulate the XML manually. Instead, inkex offers an object-oriented interface to all the SVG element types.

Each element has a style attribute: it’s one of the WRAPPED_ATTRS of each element, so is a Style object (you can think of it as a dictionary). And in this dictionary, we set the value for 'fill' to 'red'. We also set the 'fill-opacity' to 1, in case the object was transparent previously.

Final Step#

That’s it! There’s no need to set, save or do anything else as we’ve modified the style in place.

Save your python script, and re-launch Inkscape. If inkscape was already open, close it first. You should find your new extension available in the Effect menu.

Draw some shapes in Inkscape. Select some of the shapes and use the extension. The fill of all objects should change to red.