A simple node server that pipes http-received data (from canvas) to ffmpeg to create videos

1. You need ffmpeg executable installed on your machine
2. Edit init and draw in drawing.js, or just modify drawing.js and index.html freely
3. Run node pipeserver.js to start the server. The port is specified in pipeserver.js by port = 8081.
4. Open http://localhost:8081 with your browser. Or whatever port you chose.
5. Click Preview Animation to run your animation only, or click Render to pipe the animation to ffmpeg frame-by-frame
6. Check the folder for any output files

• The canvas is defined with size 1920x1080. Changes to cx and cy in drawing.js will NOT reflect to the canvas. Edit the <canvas> element in index.html instead.
• Whatever you specify in the fps input box, the preview animation will run at a fixed framerate of approximately 30 fps. Search for calls to requestAnimationFrame in index.html.
• The animation during rendering process runs at maximum speed (drawing, POSTing, piping and ffmpeg processing). The designated fps will be reflected in the output video.
• Therefore, you should NEVER rely on fps to retreive images from sources like <video>
• Sound is not currently supported. You might want to add soundtracks to the file later, or write something to pipe WebAudio to FFMPEG before I do (send me a link, thanks, lol).
• The program runs by sending PNG sequences, which might crash certain versions of FFMPEG due to an issue. Check your version and either upgrade it or modify the toBlob call in index.html
• More information about FFMPEG can be found on ffmpeg.org

This is a simple code snippet dedicated to the public domain. You can do whatever you like with it.