Hey! Thanks for reading my article and I am glad you liked it 
Saving is difficult with current code because we are not changing the original pixels of the base image. As mentioned my Christian Heilmann in the GitHub issue, to facilitate saving we need to move the functionality to canvas. I’ll work on it and post the code on GitHub and also in this article’s comment section.
One dirty way would be capture screenshot, but I would NOT recommend that. I’m planning to build something which will allow you to get new image of the size of the original.
You might find this very helpful in the meantime: https://github.com/meltingice/CamanJS/