Subtract paths, automated (using a script)

Question

I have 100+ SVG files, each containing a few closed paths (with Bezier curves), like this:

I'd like to do the following:

1. select the first (bottom) path
2. duplicate it
3. move the duplicate by an (x, y) amount

4. subtract the duplicate from the original path.

And save the SVG.

Is there any way I can do this automatically?

Technologies I looked at:

• Inkscape - as far as I can see, you can only write scripts in Python that manipulate the SVG node hierarchy directly, can't call the built-in path subtract function.
• Illustrator - I tried to record the steps in an Action, but can't seem to be able to select the bottom path automatically, you can only select objects in an Action by name.
• Affinity Designer - not scriptable.
• CorelDRAW - messed up the width / height of the SVG straight away, didn't look further.
• Scribus - superb scriptability with Python, but can't seem to find the Python function for the subtract path operation (all the other steps work).
• Clipper library (C++, C# and Delphi) - doesn't support curves, only straight lines + you would need to write the SVG parsing yourself.

I'm looking for a solution using any scriptable vector editing tool, plugin, or programming language + library combo.

Answer 1

You should be able to do this using the Illustrator actions with an odd trick.

This would work assuming the shapes in your files are of a different color as shown in your provided image.

1. Start recording your action.
2. Add a rectangle and give it a stroke (You will delete this later)
3. With your new rectangle still selected click Select -> Next Object Below
4. Click Select -> Next Object Below several more times
5. Click Object -> Transform -> Move and set your desired offset
6. Click the copy button in the move dialog
7. Click Select -> Same -> Fill & Stroke
8. Click Subtract in the Pathfinder toolbox
9. Click Select -> Next Object Above several times
10. Hit your delete key
11. Save the document
12. Stop recording the action

You can then use the batch scripting to run it on all of your files.

Answer 2

In Inkscape, you can also call verbs from commandline.

The only problem is that they don't take parameters (yet) so you can do for instance stuff like

inkscape --select=rect3680 --verb=EditDuplicate --verb=SelectionInset --select=rect3680 --verb=SelectionDiff --verb FileSave --verb FileQuit drawing-2.svg

but the "3. move the duplicate by an (x, y) amount" is actually the hardest part

Answer 3

Maybe whit this solve the problem: https://two.js.org/