What is paper.js

Paper.js, which is online at paperjs.org, is a client client-side library for working with the Canvas element.

If you want to draw graphics on a web page “on the fly”, and/or allow manipulation of graphics right in the browser, paperjs may be the tool you want.

Example of paper.js with Flask

Here is an running example on Heroku: https://spis16-webapps-paperjs.herokuapp.com/

And here is the repository of code that makes that example work: https://github.com/ucsd-cse-spis-2016/spis16-webapps-paperjs

Alternatives to paper.js

Another option is processingjs, which is a browser-based implementation of a programming language known as Processing (online at processing.org)