openFrameworks is an open source toolkit designed for "creative coding". OpenFrameworks is written in C++ and built on top of OpenGL. Developed by Zach Lieberman, Theodore Watson, and Arturo Castro, with help from the OF community.
License: Open Source
Processing.js is primarily targeted at web-based applications and is easier for beginners, making it ideal for simple projects. In contrast, OpenFrameworks is a more powerful and flexible toolkit suitable for complex and high-performance applications, but it demands a deeper understanding of programming concepts.